Makes about 3 cups
Make-Ahead: The dip can be prepared up to 1 day ahead.

Fondue works best for short-term parties; if it isn't stirred often, it can scorch on the bottom. This dip has many of the same flavors as fondue, but can be kept warm without any reservations.

1 tablespoon unsalted butter
1 small onion, chopped
1 tablespoon brandy
1 cup mayonnaise
2 cups (8 ounces) shredded Swiss cheese
1/2 cup freshly grated Parmesan cheese

1. Position a rack in the center of the oven and preheat to 350°F.

2. Heat the butter in a small skillet over medium heat. Add the onion and cook, stirring often, until translucent, about 3 minutes. Remove from the heat and stir in the brandy.

3. Mix the mayonnaise with the Swiss and Parmesan cheeses in a medium bowl. Stir in the onion. Transfer to a 1-quart heatproof serving dish. (The dip can be prepared up to 1 day ahead, covered and refrigerated. If chilled, increase the baking time.)

4. Bake until the dip is bubbly, about 30 minutes. Serve hot.

What to Dip
Fresh baguette slices
Broccoli and cauliflower florets, blanched until crisp-tender
Carrot sticks
Celery sticks
Cherry tomatoes
Cucumber slices
Tiny new potatoes, cooked
Zucchini slices