Preheat your oven to 400°F (200°C).
Melt the butter in a large skillet over medium heat. Add the onion, carrots, and celery, then cook for 5–7 minutes until softened.
1 cup carrots, ½ cup onion, ⅓ cup butter, 1 cup celery
Stir in the flour, garlic powder, onion powder, and thyme. Cook for 1–2 minutes, stirring constantly.
⅓ cup all-purpose flour, 1 teaspoon garlic powder, 1 teaspoon onion powder, ½ teaspoon dried thyme
Slowly whisk in the chicken broth and milk. Continue cooking until the sauce thickens and becomes smooth.
1½ cups chicken broth, 1 cup milk
Add the shredded chicken and peas. Season with salt and pepper, then remove from heat.
2 cups cooked chicken, 1 cup frozen peas, Salt and black pepper
In a bowl, combine the biscuit mix, ½ cup milk, and ¼ cup shredded cheddar cheese. Stir until a soft dough forms. If needed, add a splash more milk.
1 package Cheddar Bay Biscuit mix, 1 cup + ¼ cup shredded cheddar cheese, ½ cup milk
Pour the chicken filling into a greased baking dish.
Drop spoonfuls of the biscuit dough evenly over the top. Sprinkle with the remaining cheddar cheese.
Bake for 25–30 minutes, until the biscuits are golden brown and the filling is bubbling.
Mix the melted butter with the biscuit seasoning packet (or fresh herbs if preferred). Brush over the warm biscuits before serving.
2 tablespoons butter
Let cool slightly, then serve warm.