Preheat the grill to high.
To make the mushrooms, place the olive oil into a small frying pan over a medium heat.
Wrap one strip of smoked streaky bacon around each mushroom and seal with a toothpick. Add the wrapped mushrooms to the frying pan and cover with a foil lid. Cook for six minutes, shaking the pan occasionally. Once cooked, remove from the heat and set aside.
Place the 150g/5Â½oz spinach in a microwave-safe bowl with the water. Cover with cling film and cook in the microwave on full power for two minutes. Remove and set aside.
To make the pesto, place the 55g/2oz spinach, olive oil, garlic and pine nuts in a food processor and blend together. Season, to taste, with salt and freshly ground black pepper and transfer to a serving bowl.
Place the wilted spinach on top of the cooked mushrooms and place an egg yolk on top of each. Season, to taste, with salt and freshly ground black pepper and place under the grill for one minute, or until the yolk is cooked to your liking.
To serve, place the mushrooms on a plate and drizzle with pesto.