Heat the oven to 350F. This recipe works best in a 3.5 – 4 quart oven-safe skillet. If you don’t have an oven-safe skillet, you can transfer the mixture to a ~4 quart casserole dish for baking instead.

Get your ingredients ready.

Heat the oil and butter over medium-high heat in your oven-safe skillet or braiser. Add the onion and mushrooms and cook until starting to soften – about 5 minutes.

Add the ground beef and season lightly with salt and pepper. Cook until browned, breaking up the meat as it cooks. Stir in the tomato paste and seasoning.

Reduce the heat to medium-low. Sprinkle the flour over the beef and vegetables, stirring until no more dry spots are visible. Pour in the chicken broth, stirring until smooth.

Stir the potatoes into the ground beef mixture. Bring to a simmer once, then reduce the heat to a low simmer. Cover with a lid and simmer until the potatoes are halfway tender, about 10 minutes.

Whisk the half-and-half with the cornstarch, then stir into the skillet. Stir in ½ cup shredded cheddar, and top the casserole with the remaining cheese.

Bake the casserole for 25-30 minutes, until the edges are bubbly, the top is golden and the potatoes are tender.

Let the casserole sit on the counter for 10 minutes to allow the gravy to thicken, then serve.