Heat half the oil in a skillet over a medium heat. Add the bacon and cook through completely until golden. Set aside to cool, then roughly chop or crumble into small pieces.
Step 2
Preheat the oven to 350 degrees Fahrenheit. Wipe the mushrooms clean and carefully remove the stalks. Use a teaspoon to carefully scoop the gills from the center of the mushrooms and discard. Brush the mushrooms all over with the remaining oil.
Step 3
Add the mayonnaise, cream cheese, chopped bacon, and grated cheddar to a mixing bowl. Crush the garlic and roughly chop the scallions. Add the garlic and scallions to the bowl and season with salt and pepper. Stir well to combine.
Step 4
Divide the creamy cheese and bacon mixture evenly between the mushrooms. Transfer to the oven and bake for 12 minutes or until the mushrooms are tender and the filling is piping hot through and golden on top.