Prepare the pastry crust according to the recipe directions (note: the recipe will yield 2 crusts. Feel free to either half the recipe or freeze the second half for a later time).: The smell of warmed butter and whole wheat from the crust signals that it will crisp beautifully in the oven; when fitting dough into the plate you should feel it relax as you press, making it easy to crimp; this step matters because a properly prepared crust prevents leaks and sogginess; one common mistake is stretching the dough too thin which can cause shrinkage during blind baking, so if it resists, let it rest a few minutes to relax gluten before continuing.
Preheat the oven to 425 degrees F. Roll the dough into a 12-inch circle, then fit it into a 9-inch pie plate (not deep dish). Trim the crust so it overhangs the plate edge by about 1 inch all the way around, then tuck the edges under at the plate edge and crimp with your fingers or a fork.: You will notice the kitchen warming and the dough taking shape visually, with the edges overhanging by about 1 inch; rolling to an even thickness helps the crust bake uniformly, and tucking edges under creates a neat rim; avoid using a deep dish plate because it alters baking time and can leave the center underdone.
Prick the bottom of the crust all over with a fork at 1/2-inch intervals, then line the plate with foil or parchment paper. Fill with dry beans, uncooked rice, or pie weights, ensuring that the beans or weights are all the way up against the edges of the pan. Set on a rimmed baking sheet, then bake for 15 minutes. Remove the lining and weights. If the crust has puffed up in spots, gently press it back down with a fork. Bake, uncovered, for 8-10 additional minutes, until the bottom of the crust is lightly golden. Remove from oven and set aside. Reduce the oven temperature to 375 degrees F.: The gentle rattling of the weights settling in signals they are distributed to hold the crust; blind baking ensures the bottom cooks through, preventing a soggy base when the custard is added; a troubleshooting tip is to press down any puffed spots immediately after removing the weights so the custard contacts the crust; failing to blind bake typically results in a wet bottom.
Meanwhile, place the sundried tomatoes in a small bowl and cover them with boiling water. Let sit for 5 minutes to rehydrate, then drain and pat dry.: Visually you want a pale golden color and a firm base when tapped; this timing sets the stage for a crisp foundation that contrasts the soft filling; if the center looks pale but the edges are browning too quickly, tent the edges with foil; a common error is rushing this step which leaves the bottom limp and soggy once filled.
In a large bowl whisk together the eggs, egg whites, milk, Greek yogurt, pesto, salt, and pepper. Then, stir in the spinach, Parmesan, and sundried tomatoes.: The oven will settle into a gentler heat for even cooking of the custard without over browning the crust; this adjustment is crucial because the initial high heat sets the crust structure while the lower temperature cooks the filling more gently for a custard texture; do not skip lowering the oven as a hotter final bake can cause excessive rise and crack the custard.
With the pie plate still on the baking sheet, carefully pour the filling into the prebaked crust.: You will hear the quiet trickle as you drain them and feel the tomatoes plump slightly under your fingers after rehydration; this softening brings out their sweet tang and prevents them from drawing moisture from the custard during baking; a mistake to avoid is using oil packed tomatoes without draining thoroughly, which can add unwanted oil to the filling and affect set.
Bake until the quiche is puffed and the center is set but still a little jiggly, 40 to 50 minutes. If the crust starts to brown too quickly as the quiche bakes, wrap the edges of the pan with foil to protect it. Let quiche cool on a wire rack for 15 minutes. Slice and serve warm or at room temperature.: As you whisk, you will see the custard lighten in color and smell of herb and dairy emerging from the pesto; folding in the spinach and Parmesan cheese distributes texture and savory notes evenly; this technique matters because over mixing can incorporate too much air, causing the quiche to puff unevenly; avoid adding wet greens that are not well drained, as excess water thins the custard and prolongs bake time.
With the pie plate still on the baking sheet carefully pour the filling into the prebaked crust: The filling should glide into the crust and settle with minimal splashing, and you may hear a faint whisper as it levels; keeping the plate on a baking sheet catches any spills and makes transferring to the oven safe; this step is important to keep the oven clean and prevent tipping; a common slip is overfilling, so leave a little room for the custard to expand as it heats.
Bake until the quiche is puffed and the center is set but still a little jiggly 40 to 50 minutes: Watch for the quiche to develop a gentle dome and for the edges to take on a warm golden tone, while the center should wobble slightly when nudged, signaling a perfect set; if the crust browns too quickly, wrap the pan edges with foil to protect them; avoid jarring the oven during this long bake which can cause the custard to collapse and become grainy.
Let quiche cool on a wire rack for 15 minutes slice and serve warm or at room temperature: As it cools you will notice the scent of basil and cheese deepen and the quiche calming into neat slices, which makes cutting easier and cleaner; cooling allows residual heat to finish the set without overbaking; a common oversight is slicing immediately which can cause the custard to crumble, so give it the brief rest it needs.