✓ Preheat oven to 400°F (205°C). Cut the frozen French fries into smaller pieces if necessary.

✓ In a large pan, melt half of the butter over medium heat. Add the cut French fries and cook until golden brown and crispy, about 10 minutes.

✓ While the fries are cooking, separate the egg whites from the yolks. In a small bowl, mix the yolks with lemon juice and mustard.

✓ In a double boiler or a heatproof bowl set over a pot of simmering water, whisk the egg yolk mixture until thickened, about 5 minutes.

✓ Remove from heat and gradually stir in the remaining butter, one tablespoon at a time, while continuously whisking to prevent lumps. Season with salt and pepper.

✓ Add the cooked fries to the pan, toss with cheese curds, and serve hot with the hollandaise sauce drizzled on top.