Preheat oven to 425°F (220°C). Cut the potatoes into 1/4-inch fries, pat completely dry, then toss with the olive oil, chili powder, smoked paprika, garlic powder, onion powder, cumin, salt, and cayenne until fully coated.

Spread in a single layer across 2 sheet pans. Bake for 25 to 30 minutes, flipping once at the 15-minute mark, until the edges are crisp and golden.

With about 10 minutes left on the fries, melt the butter in a small saucepan over medium heat. Whisk in the flour and cook for 1 minute until pale gold, then gradually whisk in the milk and stir for 3 to 4 minutes until the sauce coats the back of a spoon.

Remove the saucepan from heat. Stir in the shredded cheddar a handful at a time until smooth, then add the chili powder, smoked paprika, and salt.

Pile the fries on a plate, pour the cheese sauce into a ramekin alongside, drizzle a little extra sauce over the top, and finish with a pinch of chili powder and smoked paprika.