Sweet caramelized onions in a rich beef broth topped with toasty bread and broiled cheese... what could possibly be better? Making it with your own Homemade Beef Stock and Demi-Glace, of course! 

Preparation

Melt butter in a large, stainless steel stock pot over medium-high heat until foaming. Add onions and cook, stirring occasionally, until softened, about 8 minutes. Lower heat to medium-low and cook, stirring frequently so the juices on the bottom don't burn, until onions are very sweet and a rich golden-brown color, about 2 hours. Season with salt and pepper.

Add sherry and bring to a simmer, scraping up any browned bits from the bottom of the pot. Cook until alcohol smell is gone, about 3 minutes. Add stock, thyme, and bay leaf, raise heat to medium-high, and bring to a simmer, then simmer on low for 20 minutes.

Discard thyme sprigs and bay leaf, add glace de viande and apple cider vinegar, and season with salt and pepper.

Preheat broiler and adjust oven rack to top position.

Butter toasts and rub with garlic clove until fragrant. Spoon a small amount of soup into the bottoms of 4 ovenproof serving bowls, then top each with a toast. Sprinkle some grated cheese on top, then spoon more soup over the top, nearly filling the bowls. Set remaining toasts in bowls, pushing to nearly submerge them, and top with remaining grated cheese

Set bowls on a baking sheet, then broil until cheese is melted and browned. Garnish with chives and serve.