Preheat broiler to high, and set a rack 6 inches from the heat.
Break eggs into a small bowl. Use a fork to beat them like a back-talking bass drum until completely blended and slightly frothy. Stir in half the pepper and half the salt.
Heat olive oil in an 8-inch cast-iron skillet over medium-high. Add mushrooms to pan; sauté 4 minutes or until nicely browned. Stir in kale and remaining salt and pepper; sauté 30 seconds or until kale is just wilted. Add eggs; stir slowly and tilt the skillet a few times so runny parts hit the pan. After about 2 minutes, when the eggs are lightly browned on the bottom with a few shiny spots still on top, sprinkle with cheese.
Place pan under broiler; broil 1 minute or until cheese softens and golden-brown spots appear on egg. Slide frittata onto a plate.
Choose Your Own Pan
Do you like the low cost of nonstick pans? Are you ok with replacing them every now and then?
You need: Tramontina ProLine 8-inch fry pan. The commercial-grade surface is as durable and stick-proof as you're likely to find, at a price point that's hard to beat. At Costco, a two-pack set (8- and 10-inch) is $25.
Do you hate replacing pans? Are you serious enough about eggs to season a pan you can use for a lifetime?
You need: Mauviel M'Steel 8-inch round frying pan. The carbon steel needs seasoning and light upkeep, but gives you a durable, oven-safe nonstick pan. $40, mauvielusa.com