Preheat the oven to 400°F.
On a baking sheet, lay bacon across in strips and transfer to the oven to cook for 8-10 minutes. You want the bacon to be cooked halfway through before adding it to the muffin tins. This can also be done in a pan on the stovetop if you like.
While the bacon is cooking, grease each muffin tin with a tiny drizzle of olive oil and use your fingers to ensure the entire muffin cup is coated in oil.
Once the bacon is partially cooked, remove it from the oven, transfer it to a plate and allow it to cool for 1-2 minutes until it has cooled enough to handle.
Once bacon has cooled, line each muffin tin with a strip of bacon, wrapping it around to line the sides.
Once each muffin cup has been lined with bacon, separate mushrooms evenly across them and season with a pinch of salt and pepper.
Gently crack one egg into each cavity and, once all eggs are cracked, transfer the muffin tin to the oven and bake for 15 to 20 minutes until the eggs are set in the middle.
Remove from the oven, allow cooling slightly, and then use a spoon to remove them from the tin.
Muffins can be stored in the fridge for up to 3 days.