I've never actually made a frittata before making this Hearty Spinach Beef Frittata from Stupid Easy Paleo. Why? Probably fear of learning that my cast iron skillet's seasoning wasn't up to snuff. For a long period of time, I made some egg muffins in silicone muffin cups, but never in metal pan. I've read many articles and watched many videos about seasoning cast iron and have seasoned mine as best I can, but I still feel that it's deficient as the surface doesn't appear as smooth as those I see on other blogs. My confidence was further brought down after I had to start over with seasoning after I made a very acidic dish in it (Don't do that!) This frittata would put my re-seasoned skillet to the test.
After gathering my ingredients and turning the oven on to pre-heat, I started by slicing the mushrooms. The recipe calls for 4 ounces of shiitake mushrooms. For me this was 6 mushrooms. I had already diced a bunch of onions for use over the week, so I only had to measure them. The recipe calls for 1 small onion so I measured out 1/2 cup of my pre-diced.