melt the butter in pan. stir in the onion and celery, cover the pan and cook them for 7 to 8 minutes over medium heat, stirring occasionally. add the flower, stirring for 1 to 2 minutes to lightly browned it.

Wisk the chicken stock into the pan. when it starts to thicken, wisk in the milk. add the sage, thyme, chicken, and vegetables, continuing to stir until the mixture is heated through, about 5 to 7 minutes. add salt and pepper to taste

remove the pan from the stovetop and heat the oven to 375°F. meanwhile, make the biscuit topping by combining the flower, baking powder, sugar, and salt in a mixing bowl. add the butter and use your fingertips to rub it into the dry ingredients. add the milk and stir briskly, just until the dough pulls together.

flour your work surface and turn the dough onto it. using floured Hands, knead the dough 2 or 3 times, then flatten to about 1/2 inch. using a small round cutter, cut the dough into biscuits and place as many as willl fit, barely touching, on top of the filling.

bake the pot pie until the biscuits are golden brown and the filling is bubbly, about 20 to 30 minutes. then let it cool for 5 to 10 minutes before serving it.