Gluten-Free Beef and Potato Casserole

Preheat the oven to 350 degrees F (175 degrees C). Spray a 9x13-inch baking pan with cooking spray.

Pierce potatoes with a fork. Microwave until fork-tender, about 12 minutes.

Meanwhile, heat a pan over medium heat. Add olive oil; cook onion until translucent, about 4 minutes. Add garlic and cook for 1 minute. Add ground beef, increase heat to medium-high, and cook until browned, 5 to 7 minutes.

Blend 1/2 cup milk with cornstarch in a small dish using a fork until well mixed and no lumps remain. Pour into the pan along with remaining milk, 1 teaspoon salt, pepper, and thyme. Reduce heat to medium and cook until thick and bubbly, about 5 minutes.

Carefully remove potatoes from the microwave with tongs. Cut into 1/4-inch slices. Place slices in the bottom of the prepared baking pan and sprinkle with 1/2 teaspoon salt. Pour ground beef mixture on top. Cover with Cheddar cheese.

Bake in the preheated oven until cheese is melted, 10 to 15 minutes.