•Melt butter in heavy large saucepan over medium heat. Add onions and garlic and sauté until the onions are tender and very brown and carmelized (about 40 minutes). Add the Flanders Red Ale to deglaze the pan and simmer about 3 minutes. Combine beef broth and mustard and add to the saucepan. Simmer about 35 minutes. Add truffle oil and season to taste with salt and pepper.
•Preheat broiler. Ladle soup into broilerproof bowls, making sure there is room for the toast and cheese. Top each bowl with slice of toast and grated cheeses. Broil until cheeses melt, brown and bubble. Enjoy with a Flanders Red Ale or for a completely different but equally delicious pairing, try a peppery and citrusy Belgian Saison! Get more tips and recipes from Cristina at: www.cristinaferrarecooks.com.