Lemon Curd (may also use store-bought): Whisk egg and egg yolk in medium bowl, set aside. Melt butter in medium metal or glass bowl set over large saucepan of simmering water. To this metal bowl, whisk in sugar, lemon juice, lemon zest, and salt; gradually whisk in egg mixture. Whisk until thick and thermometer inserted into curd registers 170°F to 175°F (it will continue to thicken upon standing). Transfer to small bowl. Cover with plastic wrap and freeze 30-45 minutes (until cold) or refrigerate for up to 24 hours in an airtight container until ready to use.: When the curd is heating over the simmering water you will notice the aroma of lemon brighten the kitchen, and the mixture will take on a velvety sheen as you whisk. The reason heating gently in a double boiler is important is to avoid scrambling the egg while allowing the sugar to dissolve and the curd to thicken slowly to the right custard like texture. Watch for the thermometer to reach 170°F to 175°F, that temperature gives you a curd that will cling to a spoon without breaking apart. One common mistake is rushing the heat, which can yield a grainy curd, so keep the water simmering but not boiling and whisk constantly to maintain a smooth emulsion.
Strawberries: Using potato masher, mash 2 cups strawberries in a large bowl. Cut all remaining strawberries into 1/4 inch thick slices. Stir sliced strawberries and sugar into crushed strawberries. Refrigerate mixture until sugar has dissolved and strawberries are juicy, at least 30 minutes up to 24 hours. The longer the strawberries chill, the more juices they release. If you chill closer to 24 hours, you may need to drain off some excess juices although you definitely keep some (seeps into the biscuits – yum!).: As you mash two cups of strawberries with the potato masher, you ll hear soft crushing sounds and smell a burst of sweet berry perfume, signaling juices releasing. The mashed berries form the syrupy base while the remaining sliced berries provide texture and bright pockets of fruit. Letting them sit with sugar for at least thirty minutes allows the sugar to draw out juices and soften the fruit but avoid letting them sit too long or they will become overly soft; if they produce too much liquid, drain a bit to prevent soggy biscuits. A common pitfall is slicing too thinly which causes the berries to disintegrate when combined, so aim for firm quarter inch slices.
Biscuits: In a large bowl, whisk half-and-half and whole egg together. Set aside.: Mix half and half and whole egg : When you whisk the half and half with the egg , you re creating a rich liquid that helps bind the dough and add tenderness. The blended liquid should feel cool to the touch and pour smoothly; this temperature helps keep the butter cold when combined with the flour. If the liquid is too warm the frozen cubes of butter will start to soften prematurely, so pause if your kitchen is warm. A frequent error at this stage is overheating the liquid which undermines the flaky layers, so keep everything chilled.
In food processor, pulse flour, 3 tablespoons sugar, baking powder, and salt until combined, about 5 pulses. Scatter butter over top and pulse mixture until it resembles coarse meal, about 15 pulses. Stir flour mixture into half and half/egg until large clumps form. Form the dough into a ball and place on a lightly floured surface, parchment paper, or nonstick mat.: Pulse flour mixture with butter : As you pulse the flour , sugar, baking powder, and salt with the cold cubed butter the mixture will go from powdery to a coarse meal dotted with pea size lumps, a texture that indicates trapped cold fat ready to create steam in the oven. This step matters because those little bits of butter form the layers in the baked shortcakes. If you over process and create a uniform paste, you ll lose flakiness, so stop pulsing once you see varied crumbs and bits of butter.
Pat dough into 9×6-inch rectangle about 3/4 inch thick. Using floured 2 1/4 inch round cutter (you can use the top of a glass), stamp out 6 dough rounds. Reshape dough and cut out 2 more. Space rounds at least 1 1/2 inches apart on parchment paper or nonstick mat lined baking sheet. Refrigerate for 20 minutes.: Combine dough and form rectangle : When you stir the flour mixture into the cold liquid, large clumps should form rather than a smooth homogeneous dough; these clumps mean the dough has pockets of fat and air which produce lift. Transfer to a floured surface and press gently to retain those clumps while shaping; the dough should feel slightly tacky and cool under your hands. Working too long will warm the dough and flatten the rise, so be swift but gentle in shaping to the nine by six rectangle.
Preheat oven to 425 degrees F.: Cut rounds and chill : As you stamp out rounds, a clean edge indicates proper pressure and a sharp cutter, and you ll hear a soft click. Spacing them on the parchment gives air circulation and chilling the rounds for twenty minutes firms the butter so the biscuits bake with better layers. A common oversight is twisting the cutter which can seal edges and prevent even rising, so press straight down and lift straight up to keep the rounds uniform.
Brush tops of rounds with egg white and sprinkle evenly with remaining 2 tablespoons sugar (it will seem like a lot of sugar but is SO good). Bake at 425 degrees F for 12-14 minutes or until tops of biscuits are golden. Transfer biscuits immediately to wire rack to cool. If not using immediately, store in airtight container once cooled.: Preheating until the oven is at a steady high heat ensures the biscuits receive an immediate burst of temperature that lifts and browns them. You ll notice a warm, toasty smell as the oven reaches temperature which signals readiness. Skipping a full preheat can cause weak rise and dense texture, so give the oven enough time to stabilize.
Lemon Curd Whipped Cream: Beat heavy cream, sugar, and vanilla extract on medium low for 1 minute. Increase speed to high and whip until medium peaks form, about 3 minutes. Gently fold cooled Lemon Curd into Whipped Cream until completely combined.: Brushing with lightly beaten egg white gives a glossy finish and helps the sprinkling sugar caramelize into a crisp top, adding contrast to the tender interior. During baking you ll hear faint crackles and the tops will acheive a golden color which is your visual cue they are done, usually twelve to fourteen minutes. Remove immediately and transfer to a rack so steam escapes, preventing soggy bottoms; leaving them on the hot sheet will continue cooking the base and can dry them out.
Assemble: Split each biscuit in half and place biscuit bottom on individual plates. Spoon equal portions of strawberries onto biscuits followed by dollops of Lemon Curd Whipped Cream, then place biscuit tops. Serve immediately.: While whipping the chilled heavy cream with sugar and vanilla extract , you ll first notice a soft, billowy texture then a firmer structure as medium peaks form. Folding the cooled lemon curd into the whipped cream adds tang and color swirls, creating a silky, lemon kissed cream that holds shape without being heavy. Overwhipping is a typical mistake, which can lead to grainy or curdled cream, so stop once medium peaks form and fold gently to maintain airiness.
Assemble: As you split each biscuit, the exposed interior should show light, layered crumb ready to absorb some berry syrup; spooning warm juice and sliced strawberries onto the bottom creates a succulent base and a satisfying contrast of temperatures and textures. Add a generous dollop of Lemon Curd Whipped Cream , crown with the biscuit top, and serve immediately so the layers remain distinct. If you assemble too early, the biscuits can become overly saturated, so build just before serving for the best balance between tender biscuit and juicy fruit.