Lemon Curd (may also use store-bought): Whisk egg and egg yolk in medium bowl, set aside. Melt butter in medium metal 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 178°F to 180°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.
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. Drain off excess juices (keep some) before serving.
Biscuits: In a large bowl, whisk half-and-half and whole egg together. Set aside.
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 or parchment paper.
Pat dough into 9x6-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.
Preheat oven to 425 degrees F.
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.
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.
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.