Gouda and Gruyere are amped up with white wine, brandy, and freshly grated nutmeg in this ooey gooey fondue.
Season beef with salt and pepper. Heat a heavy skillet over medium-high heat. Swirl in oil. In batches, add beef in a single layer. Cook, turning occasionally, until browned on all sides, about 3 minutes for medium-rare. Transfer to a plate; tent with parchment-lined foil.
Toss cheeses with cornstarch in a bowl until coated. Rub bottom and sides of a medium pot with garlic; discard garlic. Add wine and brandy; bring to a simmer over medium-high heat.
Reduce heat to medium. Stir in cheese mixture in batches, waiting for cheeses to melt before adding more. Cook, stirring, until melted and smooth, about 10 minutes. Season with nutmeg.
Transfer to a fondue pot set over a warmer. Serve with beef, apple, fennel, cornichons, and bread.