1. Combine prepared potatoes and milk in a large mixing bowl; using a potato masher, mash the potatoes until smooth and creamy. Set aside.
2. Heat 1 tablespoon butter and 1 tablespoon olive oil in a large skillet over medium heat.
3. Add chopped onions and cook for 2 to 3 minutes, stirring occasionally, until translucent.
4. Add spinach and garlic to skillet; season with salt and pepper and continue to cook for 2 more minutes, or until spinach is wilted.
5. Remove from heat and add spinach mixture to the potatoes.
6. Stir in cheese and lemon juice.
7. Add egg and panko/bread crumbs; stir until thoroughly combined and smooth.
8. Shape the mixture into patties.
9. Heat olive oil in a large skillet.
10. Working in batches, fry each patty on both sides until golden brown; about 3 to 4 minutes per side.
11. Transfer potato patties to a paper towel–lined plate.
12. Serve with sauces

Recipe sources [1]