1-First, in a large bowl, combine the 3¼ cups all-purpose flour, 1 tablespoon baking powder, 1 teaspoon salt, and ½ teaspoon baking soda. This mixture forms the base and ensures your biscuits rise properly.

2-Next, add 1 cup grated sharp cheddar cheese and 2 tablespoons finely chopped fresh sage to the bowl, mixing them in evenly for that signature taste.

3-Then, cut in 1 cup of very cold diced butter until the mixture looks like small peas, which is crucial for achieving those desirable flaky layers.

4-Stir in 1 cup cold buttermilk just until the dough comes together, being careful not to overmix to keep the biscuits tender.

5-On a floured surface, gently press and roll the dough into a 1-inch thick rectangle, then fold it into thirds like a letter for extra flakiness before rolling it out again to 1 inch thick.

6-Cut the dough into 12 squares and place them on the prepared baking sheet. Brush the tops with the egg wash for a golden finish.

7-Bake for about 15 minutes, or until the biscuits are golden brown. Remember to keep all ingredients cold and handle the dough lightly to maintain that perfect texture.