Sift together the flour, baking soda, baking powder, and salt until it is all incorporated.
2 1/4 Cups All purpose Flour, 2 tsp Baking Powder, 1/2 tsp Baking Soda, 1 1/2 tsp Salt
Cut the cold butter into 10-12 small pieces. Using a fork or a pastry blender, "cut" the butter into the flour mixture until the pieces are all the size of a pea.
1/2 Cup Unsalted Butter
In a separate bowl, mix together the buttermilk and egg.
1 Cup Buttermilk, 1 large egg
Pour the wet ingredients into the dry ingredients and work just until the dough comes together. Don't overmix! There may be some loose flour at the bottom of the bowl. That's okay.
Pick up the dough and place on a floured work surface or piece of parchment. Turn the dough a few times, pressing it together.
Then, pat the dough out into a rectangle with 3/4 inch thickness. With a dough scraper or knife, cut the biscuits into 8 square biscuits. Place on a baking sheet and gently separate them so that they are not touching.
Bake the biscuits at 450 degrees for 12-13 minutes, or until golden brown.
While the biscuits are baking, melt the 2 Tbsp of butter and mix together with 1 tsp thyme.
1 tsp thyme, 2 Tbsp salted butter
Once biscuits are done, remove from the oven and brush with the butter- thyme wash. Serve warm.