Make it your own - one of the beautiful things about frittata, omelet and quiche is that they are completely adaptable -- use whatever ingredients you have on hand and take advantage of what is in season near you. The custard content can also vary from milk (or alternate milk beverage) to cream to coconut as well as your cheese and herb selection.
Sauté to remove excess water - vegetables contain a lot of water, (notably: mushrooms & zucchini), sautéing them prior to baking the frittata allows much of this water to be released so that you don't end up with a soggy mess during the baking process.
Leek Prep - to prepare leeks, cut the ends off (the roots) and darker green tops (you can reserve for stock). Be sure to rinse thoroughly as leeks can be sandy. Slice the white/yellow part of the leek in half lengthwise (and then again if still large) and then chop the long pieces, widthwise.
Leek Nutrition - leeks form part of the powerful allium family together with its confrères garlic, onion and chives - a class of vegetables which are rich in phytonutrients and operate as antioxidants in the body. This is one sexy allium rich pie!
Smashing Garlic - I recommend smashing the garlic (as distinct from running it through a garlic press) for two reasons. I love the chunkier texture of the garlic and chopping/slicing the garlic cloves alone without first flattening it (smashing/crushing) will not release the allium's beneficial oils. To smash, simply use the flat side of a large knife and carefully press down on the garlic over a cutting board until it breaks/flattens somewhat. Sprinkle with sea salt which will absorb beautifully into the oils and then chop or slice the garlic.