Blanch the frozen spinach in boiling water for a few minutes. Drain, let cool slightly, then squeeze out the excess water. In a bowl, beat the eggs with salt, pepper, and 2 tablespoons of grated cheese. Pour the mixture into a baking pan lined with parchment paper and bake in a preheated convection oven at 350°F (180°C) for about 20 minutes.

Sauté the spinach in a skillet with the butter and a pinch of vegetable seasoning. Remove from heat, season with salt and pepper, and add a little grated Parmesan cheese. Place the frittata on a sheet of parchment paper, spread the spinach on top, and, if you like, sprinkle with a bit more Parmesan. Add the mozzarella, sliced thin, and the cooked ham. Roll everything up using the parchment paper and chill in the refrigerator for 10 minutes to set.

Bake at 400°F (200°C) for 10 minutes to melt the mozzarella. Slice and serve.