Preheat oven according to the frozen fries package instructions.

Spread 1 package frozen straight-cut fries in a single layer on a sheet pan. Sprinkle 1 teaspoon taco seasoning over the fries and toss to coat evenly. Bake according to package instructions until crisp and cooked through.

While the fries bake, make the cheese sauce: in a small saucepan over medium heat, melt 1 tablespoon butter. Whisk in 1 tablespoon cornstarch until smooth.

Slowly pour in 1 cup heavy whipping cream while whisking to prevent lumps. Cook, stirring, until small bubbles appear and the mixture begins to thicken.

Reduce heat to low. Add 2 cups freshly grated sharp cheddar cheese, ½ teaspoon taco seasoning, and the optional pinch of cayenne if using. Stir continuously until the cheese is fully melted and the sauce is smooth (about 5 minutes). Keep the sauce warm over very low heat, stirring occasionally.

If the 1 pound cooked taco meat is cold, reheat it until hot (microwave briefly or warm in a skillet).

When the fries are done, transfer them to a serving platter or keep them on the sheet pan. Top the fries with the warmed taco meat, then drizzle or spoon the warm cheese sauce over everything.

Serve immediately with salsa, jalapeños, guacamole, sour cream, and cilantro on the side or on top as desired.