Line a baking sheet with parchment paper and set aside. This will prevent the biscuits from sticking and facilitate easy cleanup.
In a large bowl, mix together the dry ingredients: all-purpose flour, granulated sugar, baking powder, baking soda, and kosher salt. Whisk until well combined, ensuring there are no clumps.
Using a cheese box grater, grate the unsalted butter into the flour mixture. This helps create those lovely flaky layers in your biscuits.
Transfer the bowl to the freezer while you gather the wet ingredients, about 5 to 7 minutes, to keep the butter cold.
Measure out the buttermilk and add the egg; whisk until combined. This mixture will be added to the dry ingredients.
In a small bowl, make the egg wash by whisking together the remaining egg and a tablespoon of water. Transfer both the egg wash and buttermilk mixture to the refrigerator while you prepare the dough.
Grab the bowl out of the freezer, and gently break up the cold butter. Combine it with the flour mixture, pressing the butter into the flour with your hands. The flour should change from white to a pale yellow as the butter is incorporated.
Pour in the diced strawberries and gently toss them to coat in flour. This ensures even distribution throughout the biscuits.
Add the buttermilk mixture all at once to the flour mixture. Mix until barely combined, being careful not to overwork the dough.
Lightly knead the dough until it forms one solid mass. Sprinkle your kitchen counter with flour and dump the dough onto it. Roll the dough into a 3/4-inch thickness.
Cut out the biscuits using a 2 1/2-inch biscuit cutter, yielding about 6 biscuits. Feel free to recombine the scraps and cut out 2 more biscuits.
Transfer the biscuits to the prepared baking sheet and place it in the freezer for 15 minutes. This helps ensure they maintain their shape while baking.
Preheat the oven to 400°F (200°C). After the biscuits are cold, whisk together the egg wash and bake in the oven for about 13 to 15 minutes, until they are tall and medium golden brown.
In a medium bowl, whisk together the powdered sugar, vanilla bean scrapings, a pinch of salt, and milk. The mixture should be thick but pourable.
When the biscuits come out of the oven, immediately pour the glaze over the top while they are still warm. Serve each biscuit warm for the best experience.
