Beer Cheese Soup with Garlic Butter Crostini

Name: Beer Cheese Soup with Garlic Butter Crostini
Ingredients: 3 tablespoons unsalted butter; 2 carrots, finely diced; 2 stalks celery, finely diced; 2 cloves garlic, minced; 1 small onion, finely diced; 1/2 teaspoon dry mustard powder; Pinch cayenne pepper; Kosher salt and freshly ground black pepper; 3 tablespoons all-purpose flour; 2 cups chicken stock; 2 teaspoons Dijon mustard; 1 teaspoon Worcestershire sauce; 1 bottle pale ale, such as Pabst Blue Ribbon; 2 cups shredded sharp yellow Cheddar; 1 cup shredded gruyere; 1/2 cup half-and-half; Garlic Butter Crostini, for serving, recipe follows; 1/2 baguette, sliced into 12 thin slices on the diagonal; 3 tablespoons unsalted butter, softened; Kosher salt; 1 clove garlic