First, prepare the lion’s mane mushrooms by carefully cleaning them with a damp cloth to remove any dirt or debris. Remove the tough stems and tear the mushrooms into small pieces.
In a large pot of salted boiling water, cook the bucatini pasta according to package instructions until al dente. Reserve 1 cup of pasta water before draining the pasta.
In a separate pan, melt butter over medium heat and saute diced onions until they turn translucent. Add in smashed garlic cloves and continue to cook for a few minutes. Then, add in the lion’s mane mushrooms and stir until they are slightly brown.
Pour heavy cream into the pan with the mushroom mixture, along with fresh thyme sprigs. Let the sauce simmer for 5 minutes on low heat.
Once the sauce has thickened, add in the drained pasta and toss to coat evenly. Gradually add reserved pasta water if needed to achieve desired consistency. Serve hot, sprinkled with grated parmesan cheese, and garnish with fresh thyme leaves for an extra touch of flavor.