Begin by thoroughly cleaning the mussels; remove any beards and scrub the shells under cold running water. Place them in a large pot with a small amount of water, cover, and cook over medium-low heat. Allow the mussels to steam for about 5-7 minutes until their shells open wide. Once cooked, take them off the heat, cool slightly, and remove half of each shell, discarding any unopened mussels.

In a medium saucepan, melt 100 grams of butter over medium heat, letting it gently bubble without browning. Add the minced garlic, sautéing for 1-2 minutes until fragrant and tender. Next, stir in the breadcrumbs and cook for another minute. Gradually add ½ cup of milk while stirring continuously until the sauce thickens, about 3-5 minutes. Season with ¼ teaspoon of salt, mix well, and set aside to cool slightly.

Preheat your oven to 355°F (180°C) while you prepare the mussels for baking. Line a baking tray with parchment paper or aluminum foil for easy cleanup. Place the mussel shells, filled with the meat, on the tray. Using a teaspoon, generously fill each shell with the creamy béchamel sauce you just made, ensuring each is adequately packed. Finally, grate 165 grams of quick-melt cheese over the top of the filled mussels.

Once your oven has reached the desired temperature, place the baking tray with the stuffed mussels inside. Bake for 10-15 minutes, watching closely as the cheese melts and turns a lovely golden brown. The aroma of the garlic, creamy sauce, and cheese will fill your kitchen, signalling that your delicious stuffed baked mussels are almost ready to delight your guests!