1. Bring a large pot of water to a rolling boil.
2. Season generously with salt until it's nearly as salty as the sea, then add dried pasta. Cook the pasta until just under al dente (a minute less than on its package directions), then drain the pasta and set aside.
3. Chop or pull apart the mushrooms into large, bite-sized chunks.
4. Then, heat a large skillet over high heat with a tablespoon of vegetable oil, and sauté the mushrooms for 3-5 minutes until nicely browned.
5. When they are done, add a little sherry vinegar to the pan with the mushrooms, give them a little toss, and set aside. It’s best to cook the mushrooms in 2-3 batches and not overcrowd the pan to allow them to brown evenly.
6. To start on the sauce, whisk the red miso paste and butter together in a small bowl until it comes together to form a smooth, fluffy paste.
7. In a medium saucepan, add the minced garlic and a tablespoon of oil, and stir-fry over medium heat for 30 seconds to a minute until fragrant.
8. Add in the sautéed mushrooms. Then, add in the miso-butter mixture and cream, and bring this sauce to a boil, stirring gently.
9. Finally, add the cooked pasta into the sauce, and stir until the pasta is well coated. Salt it to taste, and cook for 1-2 minutes until the pasta is al dente, then remove from the heat.
10. Portion the pasta into two bowls, and top with sliced scallions and freshly cracked black pepper.