For the Potatoes: Place sliced potatoes in a large bowl and fill with cold water. Use hands to mix potatoes and agitate water to rid potatoes of excess starch. Transfer potatoes to a colander to drain. Spread drained potatoes evenly on a large kitchen towel and pat dry. Set aside and allow to dry completely.
Meanwhile, whisk 2 tablespoons of butter with cornstarch, ¼ teaspoon salt, and a pinch of pepper in a large sized mixing bowl. Add potatoes and gently toss to evenly coat.
To Form the Potato Crust: Add remaining 1 tablespoon of butter in a large (10’’) cast iron skillet. Swirl to evenly coat the bottom of the skillet.
Starting with the long potato slices, lay potatoes slightly overlapping up the sides of the cast iron skillet. Switch to working with the coin slices of potatoes. Start at the middle of your skillet, place one slice of potato. Working in a circular motion, start adding potato slices, one at a time, slightly overlapping the previously placed potato (and laying the coins over top of the long potato slices) until the bottom of skillet is entirely covered with one layer of potatoes. Once you have a full inner circle formed, sprinkle with ½ Cup of the cheese.
Par Cook Potato Crust: Heat the cast iron skillet over medium heat and cook 5 minutes. Spray the top of the potatoes with nonstick cooking spray. Transfer skillet to oven and bake for 10-12 minutes, or until potatoes are soft.
Meanwhile Cook the Chorizo: Heat olive oil in a sauté pan over medium heat. Add chorizo and season with salt and pepper. Cook, using a wooden spoon to break up the chorizo into small crumbles, until cooked through, about 5 minutes. Use a slotted spoon to remove chorizo to a paper towel lined plate.
Add the sliced red onions to the pan and sauté until soft and translucent, about 3 minutes. Use a slotted spoon to transfer onions to plate with chorizo.
For the Eggs: In a medium mixing bowl, beat eggs with half and half and paprika. Season with remaining ¼ teaspoon salt and pepper. Set aside.
For the Frittata: Spread the chorizo and red onions evenly over the potatoes. Top with sundried tomatoes and remaining ¾ cup cheese. Pour beaten eggs over top.
Transfer skillet to oven and bake for 15 minutes. Cover skillet with foil and continue to cook until eggs are just set, about 5 additional minutes. Remove from oven, keep covered with aluminum foil and set aside to allow residual heat to finish cooking eggs all the way through, about 5-10 minutes.
Slice and serve warm or at room temperature.
Notes
*To Cook in Advance: 1. Prepare potato crust through step 6. Allow potatoes to cool to room temperature and transfer entire skillet to refrigerator. 2. When ready to cook, remove skillet from refrigerator and allow to sit on counter for 30 minutes. Transfer skillet to cold oven. Preheat oven to 300 degrees F. When oven reaches temperature remove potatoes. Continue as directed in recipe above. *You can also cook the chorizo and red onions in advance. Allow them to cool slightly, transfer to a container with a tight fitting lid and refrigerate. *Keep a close eye on the potatoes when cooking, to prevent them from burning. You may need to cover them with foil before the 15 minutes as directed in the recipe. Every oven cooks differently!