Prep: 25 minutes
Total: 1 hour
1 ½ pounds|536 grams mixed potatoes
canola oil, for frying
kosher salt, to taste
1 cup|250 ml balsamic vinegar
1/4 cup|45 grams dark brown sugar
1/4 teaspoon red pepper flakes
2 ounces|60 grams blue cheese
1/3 cup|80 grams sour cream
3 tablespoons mayonnaise
½ pound|225 grams flank steak
3 scallions, thinly sliced
1. Scrub the potatoes clean, then, using a mandolin, thinly slice into a large bowl of ice water. Soak the potatoes for 30 minutes, then drain and dry thoroughly.
2. Heat a large pot of oil until a deep-fry thermometer reads 350°F. Working in batches, fry the potatoes until crispy and golden brown, 7 to 10 minutes. Using a slotted spoon, transfer the potatoes to a paper towel-lined baking sheet and season with salt.
3. Meanwhile, place the vinegar, brown sugar, and red pepper flakes in a small saucepan and bring to a boil, Reduce the heat to maintain a simmer and cook until reduced by half, 25 to 30 minutes. Set aside.
4. In a small bowl, mix the Combine blue cheese, sour cream, and mayonnaise. Cover and refrigerate until ready to use.
5. Light a grill or heat a cast-iron skillet over medium-high. Season the flank steak with salt and pepper, and cook, flipping once, until cooked to desired temperature, around 8 minutes for medium-rare. Transfer to a cutting board and let rest for 10 minutes before thinly slicing against the grain. Quarter the slices of meat and set aside.
6. To assemble your nachos, arrange the potato chips on a serving platter. Layer the steak all over, then drizzle with the glaze. Dollop the blue cheese sauce all over and sprinkle with the scallions.