Preheat your oven to 400°F.
Pat the pork chops dry with a paper towel and season with salt and pepper on both sides.
Heat a non-stick oven safe skillet or cast iron skillet with oil over medium-high heat. Sear the pork chops on each side for 2 minutes or until golden brown. Remove from the skillet and set aside.
Decrease the heat to medium low and add the butter and sliced onions to the skillet. Cover and cook for 5 minutes.
Remove the lid, add rosemary and stir to combine. Cover, reduce heat to low and cook again for another 5 minutes making sure the onions don’t burn. Stir occasionally.
Remove the lid. Add the white wine and chicken stock (or broth) and stir to combine. Bring to a simmer, stirring occasionally.
Sprinkle in the cornstarch a little at a time and stir until the sauce starts to thicken. If the sauce doesn't get as thick as you like, continue adding small amounts of corn starch until desired thickness is reached.
Taste and adjust seasoning if needed.
Return the pork chops (along with the juices) to the skillet.
Add shredded Gruyere cheese and a slice of gouda to the top of each pork chop. Transfer the skillet to the oven and bake for 10 to 15 minutes or until the cheese is melted and the internal temperature of the pork chop is 145°F. Let rest 5 minutes before serving.