Lightly oil and line the baking tin with greaseproof paper
Preheat oven to 180c and place a rack in the centre
Gather and weigh your ingredients
Place the sliced sweet potato over the bottom of the lined tin, overlapping each other slightly.
Add the sliced mushroom and the chickpeas [garbanzos] (if using) on top of the potato
Crack the eggs into a medium bowl, add the milk and whisk thoroughly. Add the spring onion, broccoli, feta, parmesan, salt, pepper, paprika, coriander/cilantro and give the mix a good stir.
Pour the egg mixture over the sweet potatoes and mushroom. Top with foil and pop into the oven for 20 minutes.
Remove the foil, up the temperature to 200c for a further 25 (ish) minutes. It is cooked through when a knife inserted comes out clean and without any liquid.
Cool on a wire rack for 10+ minutes then carefully remove the frittata (still in the paper) to cool further on the wire rack. When its cool enough to handle, trim the edges and cut into 6 equal sized portions.