Start by dicing ½ cup of cold unsalted butter into small cubes, placing them in a bowl. Chill the butter in the freezer for 10-15 minutes.

In a large mixing bowl, whisk together 2 cups of all-purpose flour, 1 tablespoon of granulated sugar, 1 tablespoon of baking powder, ½ teaspoon of baking soda, and 1 teaspoon of kosher salt. Add 2 tablespoons of dehydrated onion, 1 cup of shredded white cheddar cheese, and ¼ cup of chopped fresh chives.

Add the chilled butter cubes to the dry mixture. Mix the ingredients until they resemble coarse crumbs.

Pour in ¾ cup of buttermilk slowly, mixing gently until the dough begins to come together.

Transfer the dough to a lightly floured surface and press it into an approximate 8x11-inch rectangle. Fold the dough into thirds, turn it 90 degrees, and repeat this folding technique three more times.

Cut the dough into 9 equal squares and arrange them on a parchment-lined baking sheet. Cover the biscuits with plastic wrap and chill them in the refrigerator for 30 minutes.

Preheat your oven to 450°F (232°C). Brush the tops of the chilled biscuits with remaining buttermilk and sprinkle them generously with flaky sea salt. Bake for 18-20 minutes.