Heat a frying pan over a medium-high heat. Cook the bacon in batches in a single layer until nice a crispy. Cut into chunky pieces with kitchen scissors and put aside on a plate for later.
Fry the sage leaves in the bacon fat for a few seconds, remove and place on paper towel to absorb excess oil. Toast the hazelnuts also in the bacon fat for a couple of minutes and set aside for later.
Bring a large pot of water to the boil and salt generously. Cook the pasta till al dente, drain well.
Meanwhile, heat butter in the same large frying pan over medium-high heat. Add the garlic and pine mushrooms to the frying pan and fry until mushrooms have softened. Add in the sage, bacon and hazelnuts and give a good stir. Season with salt and pepper. Finally add the cooked pasta to the pan and toss through well, coating the pasta with the mushroom mixture. Divide between four plates and crumble with ricotta cheese. Serve immediately.