Place the cubed potatoes in a large pot and fill with enough cold water so that they’re covered by about an inch.
Boil over high heat until the potatoes are fork-tender, 15 to 20 minutes.
Drain the potatoes and place them in a mash until they are smooth with no lumps (I use a ricer, but a potato masher or fork will work as well).
While to mashed potatoes are still warm, using your hands, mix in the cornstarch, garlic powder, salt, smoked paprika, and chili flakes.
Continue to mix until a dough forms. If the dough seems too crumbly, add 1 tablespoon of milk at a time until a dough forms.
Place the potato dough onto a parchment paper-lined sheet and flatten into a rectangle that about ¼”-inch thick.
Chill the dough in the refrigerator for 20 to 30 minutes. This helps form the dough, making cutting the fries easier.
About 5-6 minutes before you take the potato dough out of the refrigerator, heat the oil in a large sauté pan over medium-high heat.
Using a sharp knife, cut the dough into ¼”- wide strips.
When the oil is hot, fry the strips in batches until golden and crispy, 5 to 6 minutes.
Place a on a paper-towel lined plate to quickly drain excess oil then transfer the hot fries to a large, shallow pan.
Meanwhile, quickly mix the ingredients for the garlic-parmesan butter in small bowl.
If making the garlic aioli, pulse its ingredients in a small blender until smooth. Taste and adjust seasonings, if necessary. Set aside.
Pour the garlic-parmesan butter over the hot fries and gently toss to combine.
Serve immediately with a sprinkle of parsley and parmesan, and a side of the garlic aioli, and enjoy!