Place an oven rack in the center of the oven. Preheat oven to 350°F.: The kitchen will begin to warm and you may smell the faint metallic note of heating elements, signaling the oven is ready. Preheating ensures that when the bread goes in it toasts reliably and the timing for the later custard bake remains accurate. If you skip preheating, the bread can toast unevenly and the timing for the water bath step will be off.
In a small bowl, melt 4 tablespoons of butter in the microwave. Brush the melted butter onto one side of each of the bread slices. Set the bread, buttered-side-up, on a large baking sheet and bake 10 to 15 minutes, or until lightly toasted.: As the bread toasts you will notice the surface taking on a pale golden color and a faint nutty aroma from the butter. Toasting dries the exterior slightly so the slices can absorb custard without collapsing. Avoid leaving them too long or they will become hard and dry instead of providing that tender chew inside.
Place the strawberries in a bowl and sprinkle them with 2 tablespoons of the sugar. Toss and set aside.: The sugar draws out the juices from the strawberries , creating a glossy, slightly syrupy coating that will mingle with the custard. You will hear a soft, wet sound as the berries release liquid and see them glisten. Do not over macerate or the berries will break down completely and flood the pudding with excess moisture.
When the bread is toasted, reduce the oven temp. to 325°F and set a large roasting pan half-filled with hot water on the middle rack to act as a water bath. Trim the crusts off the bread and cut each slice of bread diagonally in half into triangles.: The shower of steam from the pan will gently regulate oven temperature around the baking dish, helping the custard set smoothly with no rubbery edges. A steady stream of small bubbles will not form in the custard if the water bath is present, just a calm, even heat. If the water is not hot or the pan is too shallow, you risk uneven baking and a cracked surface.
Use the remaining 1 tablespoon of butter to grease a 9 x 12-inch glass baking dish at least 1 1/2-inches deep. Line the sides of the baking dish with the pieces of bread, points up. Line the bottom of the dish with more of the bread. Stand the remaining bread, points up, wedged between the bottom slices. (Don't worry if there are some spaces in between the slices or if the pieces standing up lean over a bit.): The triangular pieces create pockets and angles that trap custard and fruit, giving varied textures. As you cut, notice how the crumb yields and exposes absorbent surfaces. Avoid compressing the slices too much while cutting, which can seal the crumb and reduce absorption.
Scatter the strawberries onto the bread and around the baking dish. Scatter half of the chocolate chips over the bread and between the slices.: Lining the pan this way creates a structured, decorative assembly that allows custard to pool between slices. The buttered edges will brown slightly and add flavor. If the bread is placed too tightly, the custard may not circulate well and interior pockets could stay dry.
In a large saucepan, heat the half-and-half and the remaining 1 cup of sugar over moderate heat, stirring to dissolve the sugar, until the mixture is hot but not boiling.: As you spread the strawberries and chocolate chips , notice the contrast of colors and the way juices begin to tint the adjacent bread. The chips will begin to soften from residual heat and nestle into corners, promising melty bites. Be mindful not to overload any one area with fruit, or the custard may have trouble penetrating evenly.
In a medium bowl, whisk the egg yolks and whole eggs to blend. Whisk in the vanilla. Remove the hot half-and-half from the heat. Whisk the hot mixture into the eggs 1/2 cup at a time, gradually warming up the egg mixture and not 'cooking' it. Pour the custard through a fine sieve into the baking dish. Sprinkle the remaining chocolate chips on top. Set the dish in the roasting pan in the oven and bake for 35 to 40 minutes, or until the custard is just set. Remove from the water bath and serve warm, at room temperature, or chilled.: You will see steam rising and smell the sweet cream as the sugar melts. Warming the liquid helps it integrate with the eggs without shocking them. Take care not to let it reach a boil, as boiling can change the cream's texture and make tempering riskier.
In a medium bowl, whisk the egg yolks and whole eggs to blend. Whisk in the vanilla: The eggs should be smooth and lightly homogeneous, with strands of pale yellow visible as you whisk. Adding vanilla now builds aromatic layers. Overwhisking can incorporate too much air, which leads to a spongy custard rather than a dense, silky set.
Remove the hot half and half from the heat. Whisk the hot mixture into the eggs 1/2 cup at a time, gradually warming up the egg mixture and not 'cooking' it: As you whisk in the warm cream you will notice the egg mixture loosening and taking on a luminous sheen. Tempering prevents the eggs from scrambling and ensures a smooth custard. A common mistake is adding too much hot liquid at once, which causes curdled, grainy texture.
Pour the custard through a fine sieve into the baking dish. Sprinkle the remaining chocolate chips on top: Straining removes any tiny bits of cooked egg and gives a uniformly silky custard that will set evenly. When poured, the custard should glide into nooks between the bread, filling pockets without overflowing. If the custard looks lumpy after straining, it likely indicates overheating earlier in the process.
Set the dish in the roasting pan in the oven and bake for 35 to 40 minutes, or until the custard is just set. Remove from the water bath and serve warm, at room temperature, or chilled: During baking you will notice the edges turn golden and the center will wobble slightly when gently shaken, a sign it is perfectly set. The aroma will become deeper, with toasted butter and warm cream notes. Overbaking will yield a dry, rubbery texture, so check for a tender jiggle to avoid this problem.