In a large pan heat your oil on medium-high heat. Once the oil is hot, saute the onions until soft.
Reduce the heat to medium and add the butter to the same pot. When melted, stir in the flour and cook, stirring constantly for 1 minute. Whisk in the milk, chicken broth, cream of chicken soup and thyme. Allow the sauce to come to a simmer and let it simmer for 1 minute to thicken. Season with salt and pepper.
Turn off the heat and transfer the vegetables and chicken to the pot, stirring until the filling is well-combined.
Pour the filling into a 13x9-inch baking dish and bake for 20 minutes. Remove the dish from the oven and top the filling with 8 (raw) biscuits. Return the baking dish to the oven and bake for an additional 12 minutes, until the biscuits are golden brown and the filling is bubbly. Cool for 5 minutes before serving.