Preheat the oven to 400 degrees.

Melt 1 tablespoon of butter in a skillet over medium-high heat.

Once melted, add in the chopped onion, and saute for 2-3 minutes until the onion begins to brown and soften.

Add in the brussel sprouts that have been sliced in half.

Mix in 1 teaspoon of garlic powder and salt and pepper to taste.

Pour the brussel sprout mixture into a casserole baking dish.

In the same skillet, add 1 cup of heavy whipping cream.

Bring the heavy whipping cream to a boil, and then add in the shredded havarti cheese. Mix until the cheese is melted and the sauce is smooth.

Add in ¾ cup of grated parmesan cheese, and whisk until the sauce is smooth and thickened.

Pour the cheese mixture over the brussel sprouts in the baking dish, and stir to combine.

Top the brussel sprouts with ¼ cup of shredded parmesan cheese.

Bake the brussel sprouts for 20-25 minutes until the top is browned, the brussel sprouts are tender and the cheese sauce is bubbling.

Enjoy!