Add 3 cups peanut oil to a Dutch oven and heat oil to 350°F.
Slice cold steak in ⅛ inch thin slices, set aside.
Cut potatoes into ¼ x ¼ inch strips.
Rinse potatoes and pat dry with a paper towel.
Shred Cotija and cheddar cheese.
Divide fries into four even groups. Drop first batch in oil, cook two minutes, and remove using a fried food skimmer, place on a paper towel-lined cookie sheet to absorb excess oil.
Allow oil to return to 350°F and place fries back in oil for five minutes.
Remove fries from oil and return them to paper towel lined cookie sheet, season with salt. Repeat frying steps with each additional batch of fries.
Place fries on oven safe vessel. Top fries with sliced steak and cheese and place in preheated oven. Bake at 400°F for five minutes, or until cheese melts.
Remove from oven. Top with a healthy amount of chimichurri and serve immediately.