In a large bowl, whisk the flour, baking powder, baking soda, and salt. Add the minced sage, thyme leaves, onion powder, and Parmesan cheese. Whisk together.
Add the butter pieces and cut the butter into the dough with a pastry cutter until only small pieces remain.
In a separate container, combine the egg and buttermilk. Whisk to break up the egg.
Pour the buttermilk mixture into the dry ingredients and combine with a fork until it forms a shaggy dough.
On a floured surface, knead the biscuit dough until it holds together. Pat into a circle about ½-inch thick.
Cut with a 2- or 3-inch biscuit cutter and place biscuits on a parchment-lined baking sheet. Continue cutting biscuits. Once the biscuits have been cut, press together the remaining dough and press to ½-inch thick to cut the remaining biscuits.
Brush the tops of the biscuits with more buttermilk.
Bake in preheated oven for 12-15 minutes until puffed and golden with a crisp top.
Remove the biscuits from the oven and brush the tops with melted salted butter. Serve immediately.