In the bowl of a stand mixer fitted with the paddle attachment, beat 1 cup (125 grams) flour, 1/4 cup (50 grams) granulated sugar, yeast, and salt at low speed until combined. Add warm milk; beat just until combined. Add 2 eggs (100 grams) and egg yolk; beat at medium-low speed until combined, about 1 minute, stopping to scrape sides of bowl. With mixer on low speed, gradually add remaining 1 1/2 cups (188 grams) flour, beating just until combined.
Switch to the dough hook attachment. Beat at low speed until dough is relatively smooth, elastic, and starts to pull away from sides of bowl, 6 to 9 minutes, stopping to scrape sides of bowl and dough hook. Add butter, 1 tablespoon (14 grams) at a time, beating until combined after each addition (6 to 8 minutes total); scrape sides of bowl and dough hook. (Dough may look slightly broken during this process but will come together.) Increase mixer speed to medium-low; beat until a smooth, elastic dough forms, 6 to 9 minutes, stopping to scrape sides of bowl and dough hook. (Dough should pass the windowpane test; see Notes.) Turn out dough onto a clean surface, and knead 4 to 5 times. Shape into a smooth round.
Spray a large bowl with cooking spray. Place dough in bowl, turning to grease top. Cover and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, 1 to 2 hours.
Line 2 baking sheets with parchment paper.
Punch down dough; cover and let stand for 10 minutes. Turn out dough onto a clean surface; divide into 12 portions (about 52 grams each). Gently shape 1 portion into a smooth ball, pinching any seams to seal. (Keep remaining dough covered with plastic wrap to prevent drying out.) Repeat with remaining portions. Press or roll each dough ball into a 3½¼-inch round; place 1½ to 2 inches apart on prepared pans. (Dough rounds may shrink slightly.) Cover and let rise in a warm, draft-free place (75°F/24°C) until puffed and dough holds an indentation when poked, 30 to 40 minutes.
Preheat oven to 350°F (180°C).
Meanwhile, in a large bowl, stir together strawberries, lemon juice, pepper (if using), and remaining 2 teaspoons (8 grams) granulated sugar. Let stand, stirring occasionally, until ready to use.
Using a ¼-cup glass jar or dry measuring cup dipped in flour, make a 2¼-inch-wide, ¼- to ½-inch-deep well in center of each dough round. (See Notes.) Divide Lemon Pastry Cream among dough rounds (about 1 scant tablespoon [about 11 grams] each), spreading to fill. Using a slotted spoon, arrange strawberries evenly on top of pastry cream as desired. (Enjoy or reserve any extra strawberries as a treat.)
In a small bowl, beat remaining 1 egg (50 grams) and milk. Brush dough with egg wash; sprinkle with pearl sugar.
Bake until light golden brown, 8 to 10 minutes, rotating pans halfway through baking. Serve warm or at room temperature.