Heat olive oil and butter in a dutch oven (oven-proof casserole) over medium-high heat. Brown chicken pieces on all sides; transfer to a plate.

Add onion, celery and cabbage to dutch oven and saute until softened. Stir in flour; cook 2 minutes. Gradually add milk and chicken broth, stirring constantly. Return chicken to pot; add potato, thyme and bay leaf. Cover and cook until potato is cooked through and stew thickens, about 20 minutes. Season well with salt and pepper.

Meanwhile, preheat oven to 400 degrees.

To make biscuit topping, whisk together flour, baking powder, baking soda and salt. Using a pastry blender (or working quickly with your fingers), work butter into flour mixture until it resembles coarse crumbs. Add buttermilk and stir until just combined.

Using two spoons, drop biscuit dough on top of stew. Bake 15-20 minutes until golden brown.