How to Make It
Preheat the oven to 425°. In a large cast-iron skillet, heat 2 tablespoons of the olive oil. Add the onion and cook over moderate heat, stirring occasionally, until softened, about 5 minutes. Add the spinach and garlic and cook, stirring, until fragrant, about 2 minutes. Stir in the milk, cream and nutmeg and cook until thickened and almost all of the liquid has evaporated, 8 to 10 minutes. Add both cheeses and season with salt and pepper; stir until well blended and the cheese is melted. Scrape into a large bowl and let cool slightly. Add the eggs and mix well. Wipe out the skillet.
In the skillet, heat the remaining 1 tablespoon of olive oil. Add the sausage and cook over moderate heat, stirring occasionally and breaking up the meat, until browned, about 5 minutes. Remove the skillet from the heat. Spread the spinach mixture over the sausage. Arrange the Tater Tots in concentric circles on top and spray with canola oil cooking spray. Bake for about 40 minutes, until the tots are golden, cooked through and crispy. Serve immediately.