Dutch Mustard Soup

Name: Dutch Mustard Soup
Ingredients: 2 tablespoons Butter; 4 cups Mustard greens, trimmed and stems removed; 2 Leeks, sliced into thin rings; 2 Garlic cloves peeled and smashed; 5 cups Veggie stock; 1 cup Dark beer; 3 tablespoons Mustard, I used Grey Poupon Dijon; 8 ounces Brie soft cheese rind trimmed and cubed; Pinch Salt and White pepper, to taste