1. Preheat the oven to 350°. In a small bowl, combine the tomatillos, red onion, cilantro and 1/2 teaspoon of the hot sauce.
2. In a medium bowl, combine the roast beef with the Fontina and the remaining 1/2 teaspoon of hot sauce. Arrange half of the tortilla chips on a large rimmed baking sheet. Spoon the roast beef filling onto the tortilla chips and top with the remaining 24 chips.
3. Bake the tostaditos for 5 to 7 minutes, or until the filling is hot and bubbling. Transfer to a platter. Season the tomatillo relish with salt, spoon a little on top of each tostadito and serve immediately.
Wine Recommendation: Stuckey: The 1993 Iron Horse Brut Rosé from California is high in acidity, which refreshes the palate after a little south-of-the-border heat.Triffon: Sweet-tart-spicy Southwestern flavors love fruity Gewürztraminer, and the acidity and slight sweetness in the 1996 Domaine Weinbach Cuvée Laurence go nicely with the tomatillos.