Par boil the sliced potatoes in some water (enough to cover the potatoes) for 5 minutes. Turn off heat. Drain water and set aside
Heat oil in an oven-proof non-stick skillet. Add in onions and garlic. Cooked until they are soft
Add in potatoes and saute until they are brown. Add in tomatoes, corn and bell peppers. Season with salt and Pepper to taste
Pour in the egg mixture into the skillet, covering the entire skillet. Let it cook for 8-12 minutes until the bottom side of the egg harden and settle. Sprinkle with fresh chopped parsley and turn off heat
Preheat the broiler and finish cooking the spanish tortilla in the broiler for 5-7 minutes
Remove from the broiler and cut into wedges or squares