Preheat oven to 200°C or 400°F fan forced.
Add onion to mixer bowl, chop for 3 sec/speed 5/MC on.
Add bacon and mushrooms to mixer bowl, chop for 3 sec/speed 5/MC on.
At this step, you can either scrape the mixer bowl down, add ghee/butter and saute for 6 min/100°C or 212°F/speed 1/MC off or transfer to the stove top if you prefer.
Spoon mixture evenly amongst 8 large silicone muffin moulds, crack an egg into each one (ensuring the white covers the bacon well), sprinkle with salt and pepper, and top with tomato slice if using.
Bake in the oven for about 20-25 min or until set firm.