Drain and pat the fries completely dry with clean kitchen towels. Dry potatoes will sizzle less and brown more evenly when they hit the hot tallow.

Heat beef tallow in a heavy pot to 325 F (163 C). You should smell a faint meaty aroma and see the surface shimmer - not smoke.

Blanch the fries in batches for 4 to 6 minutes, until they are cooked through but pale and soft to the bite. They will give off a tender potato scent and slightly creamy texture when pierced.

Remove blanched fries to a wire rack to cool for 10 minutes. Cooling firms the interior and prevents steaming during the final fry, promoting crispness.

Raise the tallow temperature to 375 F (190 C). This high temperature creates rapid steam at the potato surface and forms the crisp crust.

Fry the cooled potatoes in batches for 2 to 4 minutes, until golden brown and crackling when stirred. You'll hear a vigorous sizzle and see a deepening color at the edges.

Drain on paper or a rack, season immediately with kosher salt and freshly ground pepper, and toss gently. Seasoning while hot helps salt adhere to the fries' surface.

Serve hot, with your preferred dip. I recommend ketchup or a sharp aioli for contrast with the beefy richness of the tallow.