Preheat the oven to 200 degrees Celsius. Line a baking tray with aluminium foil for easy cleaning later on. Drizzle some olive oil on top of the aluminium foil. Clean the mushroom and remove the stems. Dry it thoroughly with kitchen paper/towel and place it on top of the greased foil.
Heat a frying pan and add the bacon (don’t add any oil!) and sautéed it until the bacon has released some of its fats. If it is too dry, add in a little bit of olive oil. A little goes a long way, so don’t add too much!
When the bacon is almost golden brown in colour, add in the onion and continue to sautéed until the onion has softened and the bacon is golden brown in colour. Season with black pepper and remove from heat.
Transfer the bacon mixture onto the mushroom. Top the mushroom with the cheddar strips and bake for 10 minutes until the cheese has melted and the mushroom is soft.