Ingredients

Cooking spray or olive oil
2 large eggs
1 tablespoon milk*
2 tablespoons finely chopped bell pepper (color of choice; see notes for options**)
2 tablespoons finely chopped ham (can omit for vegetarian option)
2 tablespoons shredded sharp cheddar cheese (mozzarella and Italian blend work well, too)
Pinch of salt and pepper
Optional for serving: salsa, chopped avocado, freshly ground pepper, hot sauce

Instructions

Coat the inside of a large, microwave-safe mug with cooking spray, or brush thoroughly with olive oil.
Add the eggs and milk to the prepared mug, and whisk thoroughly with a fork. Add the remaining ingredients (excluding the optional toppings), and stir to combine.
Microwave for 20 seconds on high. Remove from microwave and stir with a fork. Continue to microwave in 20 second increments, stirring after each burst, until just barely done. The last burst might be just 5-10 seconds. The eggs will continue to cook once removed from the microwave and will become rubbery if overcooked; the key to success is to stop cooking when they are a touch undercooked. Precise time will vary based on power of microwave and mug proportions. (See Tips.)
Cool slightly before eating—the eggs will be hot. Serve as is or top with salsa, avocado, hot sauce, etc.

The small amount of milk adds lightness to the cooked eggs and helps them cook more evenly. However, the eggs can be made without. Optionally, seltzer or (unflavored) sparkling water can be used as a substitute.
**You may experiment with this recipe, using chopped spinach in place of the bell pepper, substituting crumbled feta for the cheddar, replacing the ham with cooked and crumbled bacon, adding some sliced green onions or chives, etc. Just keep the overall proportions of add-ins to egg similar. Firmer vegetables like broccoli work better if they have been cooked first, making leftovers from last night’s dinner fair game.
Tips:
The eggs will cook first along the outside rim of the mug. When stirring, break up this area and then stir the cooked clumps into the center of the mug. This will help to cook the eggs evenly. Reducing the cooking increments to 10 seconds near the end will allow you to fine-tune the cooking process and avoid overcooking.
For an extra quick breakfast, you may mix the cups the night before, cover with plastic wrap, and cook in the morning.
As an option, you could use 1/2 cup of liquid egg substitute in place of the two eggs.