Peel the potatoes and cut them into evenly sized fries using a chef's knife on the cutting board. Rinse the cut fries under cold water and pat dry with a towel.
Heat the olive oil in a frying pan over medium-high heat until shimmering. Add the fries in a single layer and fry for about 5-7 minutes, turning occasionally, until golden brown and crispy. Remove fries from the pan and drain excess oil on a paper towel-lined plate.
While fries are frying, grate the cheddar cheese and thinly slice the jalapeños. Prepare the guacamole by mashing the ripe avocado in a small bowl and seasoning with salt and pepper to taste.
Transfer the crispy fries to a baking sheet or plate, then sprinkle evenly with shredded cheddar cheese. Place under a broiler or in a hot oven (around 375°F) for 2-3 minutes until the cheese melts and begins to bubbly.
Once the cheese has melted, remove the fries from the heat. Top with sliced jalapeños, dollops of sour cream, and spoonfuls of guacamole. Serve immediately for maximum crunch and freshness.
