Preheat oven to 375°F. Heat olive oil in a large oven-safe skillet over medium-high heat.
Season chicken with salt and pepper, then cook for 5-6 minutes until browned and cooked through. Remove and set aside.
In the same skillet, sauté onions for 3 minutes. Add diced potatoes and cook for 5 minutes, stirring occasionally.
Sprinkle flour over the vegetables and stir well. Gradually add chicken broth and milk, stirring constantly.
Add thyme, garlic powder, and frozen vegetables. Bring to a simmer and cook for 8-10 minutes until potatoes are tender and sauce has thickened.
Return chicken to the skillet and stir to combine. Top with biscuits, evenly spaced.
Transfer skillet to the oven and bake for 12-15 minutes until biscuits are golden brown. Let cool for 5 minutes before serving.