Step 1: Prepare the Filling
1. Preheat your oven to 400°F (200°C).
2. In a large saucepan, melt the butter over medium heat. Stir in the flour and cook for 1–2 minutes until bubbly and lightly golden.
3. Gradually whisk in the chicken broth and milk, cooking until the mixture thickens (about 3–5 minutes).
4. Stir in the cooked chicken, frozen mixed vegetables, garlic powder, onion powder, salt, pepper, and thyme if using. Remove from heat.

Step 2: Prepare the Biscuit Topping
1. In a large bowl, combine the flour, baking powder, and salt.
2. Add the cold cubed butter and mix until the mixture resembles coarse crumbs.
3. Pour in the milk and stir until just combined.

Step 3: Assemble and Bake
1. Pour the chicken filling into a greased 9×13-inch baking dish.
2. Drop spoonfuls of biscuit dough over the filling, leaving space between each biscuit.
3. Bake for 30–35 minutes, or until the biscuits are golden brown and cooked through.

Step 4: Serve
1. Allow the pot pie to cool for a few minutes.
2. Serve warm.