Preheat the oven to 350°F (175°C).
In a large skillet over medium heat, add butter and olive oil. Once the butter has melted, sauté garlic and pancetta until it is lightly browned.
Add onions and mushrooms to the pan and continue cooking for a few more minutes.
Place chicken thighs into the skillet and pour in Riesling. Bring to a boil and reduce heat to low. Simmer for about 20 minutes until the chicken is cooked through and the sauce has reduced slightly.
Add the cream and let it simmer for another 5 minutes, stirring occasionally.
Season the dish with pepper and salt to taste.
Place the chicken in a baking dish and pour over the sauce from the skillet.
Bake in preheated oven for 20 minutes, or until golden brown on top.
Serve hot with your favorite side dishes.