1. Preheat your oven to 375°F (190°C). Make sure it's nice and hot before moving forward.

2. Cook the macaroni according to the package instructions until it reaches a perfect al dente texture. Once done, drain the water and set the macaroni aside for later use.

3. In a large skillet, heat about 2-3 tablespoons of rapeseed oil (you can also use canola oil as a substitute) over medium heat. Add one medium-sized chopped onion and cook until it's softened and translucent, about 5 minutes. Next, add 2-3 cloves of minced garlic and cook for an additional minute, stirring constantly to avoid burning.

4. Add 2-3 boneless chicken breast fillets to the skillet and cook until they're nicely browned on all sides and cooked through. Remove the chicken from the heat and set it aside with the macaroni.

5. In a large bowl, combine the cooked macaroni, chicken, and 1 cup of chopped Brussels sprouts (that's what 'brysselkål' translates to).

6. In a separate bowl, mix together 1 cup of grated cheese (any melty cheese like cheddar, mozzarella, or a mix will work), a pinch of salt, and a few grinds of pepper.

7. Grease a 9x13 inch (23x33 cm) baking dish with some butter or cooking spray. Add the macaroni mixture to the dish and top it with the cheese mixture, spreading it evenly.

8. Bake in the preheated oven for 25-30 minutes, or until the top is golden brown and the cheese is melted and bubbly.

9. Serve hot and enjoy your delicious macaroni bake!