Stir together mashed potatoes with salt and pepper.

Set up dredging stations. In one shallow bowl add flour, salt and pepper. In another bowl, whisk together egg with 1 Tbsp water. In a third bowl, add 1 1/2 cups breadcrumbs.

Form potatoes into large balls, approximately 2" wide. Roll in flour, shake off excess and dig in egg wash. Roll in breadcrumbs to coat.

In a heavy bottomed saucepan, heat 1 1/2" vegetable oil over medium high until hot. Fry the potato croquettes in batched until golden brown on all sides, approximately 2 minutes total, turning as needed. Remove to paper towel lined plate to drain.

Stir together mayonnaise, lemon juice, chili powder, paprika and garlic powder in a small bowl. Serve croquettes with aioli on the side for dipping.