If using the one pan here, make sure to use something that can go on a cooktop, as well as in the oven. I use a pan thats 28cm x 32cm and as you can see from the images this yields a fairly thin frittata. A 23cm x 23cm (9" x 9") square pan would probably be ideal - just make note that for thicker frittatas you may need to increase the cooking tie slightly.