Preheat oven to 400 °F.
Lightly grease a 9" x 13" casserole dish.
Cook the macaroni according to the directions. Drain, and stir the cooked macaroni occasionally to prevent it from clumping together.
Brown the ground beef. Drain the fat. Season with freshly ground black pepper and set aside.
Saute the garlic in oil.
Add the kimchi and cook for 5 minutes, until the kimchi is tender. Use kitchen scissors to cut the kimchi into bite-sized pieces.
Add the mirin and crushed red pepper, and cook 2 more minutes.
Add the flour, and stir until the flour is cooked.
Add the half-and-half, 1/2 cup (115 g) at a time, bringing back to a simmer before adding the next 1/2 cup (115 g).
Simmer until there is not much excess liquid.
Add the beef.
Add the two types of cheddar cheese, and stir until melted.
Stir in the cooked macaroni until well-mixed.
Pour into the greased 9" x 13" casserole dish. Top with Parmesan cheese.
Bake at 400 °F for 15-20 minutes. The cheese should be melted and bubbling.
Remove from the oven, let sit for 5 minutes, and then serve.