Preheat oven to 375°. In a large skillet, heat butter over medium heat; saute celery and onion until tender, 4-5 minutes. Stir in vegetables, soup, milk and seasonings; heat through, stirring occasionally. Stir in chicken; remove from heat.
On a lightly floured surface, roll each biscuit into a 5-in. circle. Press each onto the bottom and up side of each of 20 greased muffin cups, allowing edges to extend above cup. Fill each with about 3 tablespoons chicken mixture. Pull up edges of dough and fold partway over filling, pleating as needed.
Bake until crusts are golden brown and filling is bubbly, 15-18 minutes. Cool 1 minute before serving.