Strawberries
Step 1
Gently mix 1 lb. fresh strawberries, hulled, cut into large pieces, zest and juice of ½ lemon, 2 Tbsp. sugar, and ¼ tsp. Diamond Crystal or Morton kosher salt in a medium bowl to combine. Let sit at room temperature at least 1 hour.
Do Ahead: Strawberries can be macerated 4 hours ahead. Cover and chill.
Choux and Assembly
Step 2
Place a rack in middle of oven; preheat to 425°. Bring 4 Tbsp. unsalted butter, cut into pieces, ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt, 1 Tbsp. sugar, and ¼ cup plus 3 Tbsp. (105 g) water to a boil in a medium saucepan, stirring with a wooden spoon to encourage butter to melt and salt and sugar to dissolve. Immediately reduce heat to medium-low and add ½ cup (63 g) all-purpose flour all at once. Stir gently until most of the flour is absorbed, then cook, stirring vigorously and breaking up pockets of flour as needed, until a thin film forms on bottom and sides of pan and dough comes together into a single mass, 2–3 minutes. (The dough should look glossy and feel buttery-slick to the touch.) Transfer dough to a small bowl and spread up the sides with spoon (this will encourage it to cool faster). Let sit until cooled slightly but still warm to the touch, about 4 minutes.
Step 3
Pour 1 large egg, room temperature, beaten to blend, into the center of bowl with dough. Using a fork, mix until incorporated, then add remaining 1 large egg, room temperature, beaten to blend, and mix again to combine. Using a rubber spatula, scrape any dough from fork, then vigorously mix dough with spatula until very smooth, glossy, and a little stretchy (when you lift the spatula out of the dough, the dough falling off the end should form a V shape).
Step 4
Using a large metal spoon, scoop out about 2 Tbsp. dough (you will be making 6 choux cakes, so you want about a sixth of the dough). Using another large metal spoon, scrape dough onto a parchment-lined baking sheet. Repeat with remaining dough to create 5 more choux cakes, leaving a generous amount of space around each one. Scrape out any bits of dough remaining in the bowl and distribute equally among choux cakes.
Step 5
Using a wet index finger, gently smooth out any pointy bits of dough (these can burn in the oven). Sprinkle each choux cake with a generous pinch of sugar and bake 10 minutes. Decrease oven temperature to 350° and continue to bake 15 minutes longer. (It’s important not to open the oven door at any point during this time—you need all that trapped heat and steam to create light-as-air choux cakes.)
Step 6
Crack oven door open and check choux cakes; if they still look pale, continue to bake until golden brown, 2–5 minutes more. Transfer to a wire rack; immediately poke a small hole into the bottom of each choux cake with a skewer, chopstick, or paring knife to let the steam escape. Let cool, right side up.
Step 7
Meanwhile, whisk 1 cup heavy cream and 1 tsp. vanilla bean paste or vanilla extract in a clean small bowl until firm peaks form. Cover and chill until ready to use.
Step 8
To serve, using a serrated knife, gently slice choux cakes in half through the equator and arrange bottom halves on plates. Spoon strawberries along with any juices at the bottom of the bowl over each choux cake bottom, dividing evenly. Scoop some whipped cream on top of strawberries and close up choux cakes.
Do Ahead: Choux cakes can be formed 1 month ahead. Freeze on a baking sheet until solid, then transfer to a resealable plastic freezer bag. Bake from frozen, increasing baking time to 15 minutes at 400° and 20 minutes at 350°.