Prepare the Potatoes: Preheat your oven to 200°C (180°C fan). Place your cut potatoes in a large bowl and cover with cold water. Let them soak for at least 20 minutes. This step removes excess starch and is key to a crispy fry.

Dry and Coat the Fries: Drain the potatoes thoroughly and pat them completely dry with a clean tea towel or paper towels. Moisture is the enemy of crispiness! Return the dry fries to the bowl, drizzle with the vegetable oil and sprinkle over the cornflour. Toss well until every fry is lightly coated.

Season and Bake: In a small bowl, mix together all the seasoning ingredients: paprika, garlic powder, onion powder, chilli powder, salt, and pepper. Spread the fries in a single layer on one or two large baking trays. Bake for 15 minutes.

Make the Roux for the Sauce: While the fries are baking, start the sauce. Melt the butter in a medium saucepan over a medium-low heat. Whisk in the plain flour and cook for 1 minute, stirring constantly, to form a paste (this is a roux).

Build the Sauce Base: Gradually pour in the whole milk, a little at a time, whisking continuously to prevent lumps. Once all the milk is incorporated, whisk in the evaporated milk. Let the sauce gently bubble and thicken for 2-3 minutes, stirring so it doesn't catch on the bottom.

Melt the Cheese: Reduce the heat to low and add the grated cheddar, a handful at a time, stirring until each addition has fully melted before adding the next. I find that doing this slowly prevents the sauce from splitting.

Finish the Sauce: Once all the cheese is melted and the sauce is smooth, stir in the jalapeño brine, smoked paprika, and a pinch of salt. Keep the sauce warm over the lowest possible heat while the fries finish.

Finish the Fries: After 15 minutes, remove the fries from the oven, flip them over, and return them to the oven for another 10-15 minutes, or until golden brown and crisp.

Combine and Serve: Remove the hot fries from the oven and immediately transfer them to a large bowl. Sprinkle over the prepared seasoning mix and toss vigorously until every fry is coated. Serve the hot Taco Bell Nacho Fries straight away in a basket with the warm nacho cheese sauce on the side for dipping.