Brush the mushrooms clean and slice them. Heat the olive oil in a frying pan and sauté the mushrooms over high heat until the liquid evaporates and they turn golden brown. Season with salt and pepper and transfer to a plate.
Melt the butter in the same pan. Crack the eggs into it and fry gently until the egg white is set but the yolk is still soft.
Slice the avocado into wedges and place them next to the mushrooms. Slide the fried eggs alongside and snip a generous handful of garden cress over the top. Grind some black pepper over it. This savory breakfast is full of protein and healthy fats.