Peel 5–6 large russet potatoes. Place the potatoes into a large pot and cover with water. Add a generous pinch of salt. Bring the water to a boil and cook the potatoes for approximately 8 minutes, just until partially cooked. The potatoes should still be firm in the center. Avoid cooking them until fork-tender because they'll become too soft to grate properly.

Carefully drain the potatoes. Allow them to cool until they're comfortable to handle. For easier grating, you can refrigerate them for approximately 15–20 minutes. Make sure the potatoes are well-drained before continuing.

Using the large holes of a box grater, shred the partially cooked potatoes into a large mixing bowl. Work gently so the potatoes maintain their shredded texture. If necessary, remove any excess moisture with paper towels.

To the bowl of shredded potatoes, add: 4 tablespoons cornstarch, 6 ounces shredded cheddar cheese, ¾ cup freshly grated Parmesan cheese, 1½ tablespoons garlic powder, 1 tablespoon onion powder, 1 teaspoon black pepper, and 1 teaspoon salt, or to taste. Gently fold everything together until evenly combined. Avoid overmixing.

Take approximately ⅓–½ cup of the potato mixture. Using your hands, firmly press the mixture into a thick rectangle or oval-shaped patty. Aim for approximately ½–¾ inch thickness. Repeat until all the potato mixture has been shaped. If the patties feel too soft to handle, refrigerate them for 15–20 minutes before frying.

Pour approximately 1 inch of vegetable or canola oil into a heavy-bottomed skillet. Heat the oil over medium heat until it reaches approximately 360°F. Use a kitchen thermometer if available.

Carefully place a few hash browns into the hot oil. Avoid overcrowding the skillet. Fry for approximately 3–4 minutes on the first side until deeply golden brown. Using a slotted spatula or tongs, carefully flip each hash brown. Continue frying for another 3–4 minutes until both sides are crispy and golden. The centers should be hot and the potatoes fully tender.

Remove the hash browns from the oil. Transfer them to a wire rack positioned over a baking sheet. Allow excess oil to drain. A wire rack helps preserve the crispy texture better than stacking the hash browns directly on paper towels. Repeat with the remaining potato mixture.

In a small mixing bowl, combine: ½ cup mayonnaise, 1–2 freshly grated garlic cloves, 1 tablespoon garlic powder, ½ teaspoon black pepper, 1 tablespoon lemon juice, and ¼ teaspoon salt, or to taste Stir until smooth and creamy. Taste and adjust the seasoning or lemon juice if necessary.

Cover the garlic sauce and refrigerate for approximately 15–20 minutes. This allows the garlic and lemon flavors to develop.

Arrange the crispy hash browns on a serving plate. Sprinkle with freshly grated Parmesan cheese and chopped parsley. Serve immediately with the homemade garlic dipping sauce. Enjoy!