First, the strawberries: In a medium bowl, toss sliced strawberries with 1/4 cup sugar and 1 tsp lemon juice. Let sit at room temperature for at least 20 minutes, stirring once or twice, until a deep red syrup forms.
Preheat and prep: Preheat oven to 425°F (220°C). Line a baking sheet with parchment paper.
Mix dry ingredients: In a large bowl, whisk together 2 cups flour, 1/4 cup sugar, 1 tbsp baking powder, and 1/2 tsp salt.
Grate in butter: Using large holes of a box grater, grate frozen butter directly into flour mixture. Toss gently with fingers to coat butter pieces in flour. Mixture should look like coarse meal with visible pea-sized bits of butter.
Add buttermilk: Make a well in center, pour in 3/4 cup cold buttermilk and 1 tsp vanilla. Stir with a fork just until dough comes together. It will be rough and scraggly – do not overmix.
Pat and cut: Turn dough onto a lightly floured surface. Pat into a 3/4-inch thick rectangle. Fold in half, pat out to 3/4-inch thickness. Repeat once more. Pat to 3/4-inch thick one last time. Cut out biscuits using a 2 1/2-inch cutter, pressing straight down and pulling straight up – do not twist.
Bake: Place biscuits on prepared baking sheet, nearly touching. Brush tops with extra buttermilk and sprinkle with a pinch of sugar. Bake for 14-16 minutes until golden brown and hollow-sounding when tapped on bottom.
While biscuits bake, make cream: In a chilled bowl, combine 1 1/2 cups heavy cream, 2 tbsp powdered sugar, and 1/2 tsp vanilla. Beat with hand mixer on medium speed until soft peaks form – billowy and thick, not stiff.
Assemble: Split warm biscuits in half. Place bottom half on a plate, spoon generous amount of macerated strawberries and juice over it, add a cloud of whipped cream, top with other biscuit half. Add another spoonful of berries and a final dollop of cream. Serve immediately.