Makes 6 servings Ingredients 2 tablespoons butter1/2 medium yellow onion, finely diced2 carrots, finely chopped2 stalks celery, finely chopped2 cloves garlic, minced1/4 teaspoon dried thyme1 tsp. Dijon mustard12 ounces broccoli florets, roughly chopped (4 cups)1/4 cup all-purpose flour2 1/2 ...