Preheat your oven to 350°F (190°C).
Dice the chicken into large cubes. In a large oven-safe skillet, heat 1 tbsp olive oil and cook chicken, with a large pinch of salt, for about 10 minutes. Remove from pan.
In the skillet, heat the other tbsp of olive oil over medium heat. Add the onion, carrots, and celery, and cook until softened, about 5 minutes. Make sure to season with more salt and pepper.
Stir in the frozen peas, and cook for an additional 2 minutes.Add the thyme then add the flour and coat the veggies.
Slowly pour the broth, then the milk. Slowly stir and add the miso. Bring to a simmer, and the chicken, and cook for 5 minutes, or until the sauce has thickened slightly.
Arrange the premade biscuits on top of the filling in the skillet.Bake for 25 minutes, or until the biscuits are golden brown and the filling is bubbling. Brush the top of the biscuits with butter if wanted. Remove from the oven and let cool for a few minutes before serving.