Bring a large pot of salted water to a boil. Add udon noodles and cook until just tender (2–3 minutes for fresh or frozen). Drain and rinse briefly under warm water. Set aside.

In a deep skillet, melt butter over medium heat. Add garlic and mushrooms. Sauté until mushrooms are golden and fragrant.

Pour in broth and bring to a gentle simmer. In a small bowl, whisk miso paste with a few tablespoons of warm broth until smooth, then stir it back into the skillet.

Add soy sauce, cream, and sesame oil, whisking to combine.

Toss cooked noodles into the sauce. Use tongs to coat evenly. Simmer for 1 minute for flavors to meld.

Taste and adjust with salt and black pepper. Garnish with green onions, sesame seeds, or nori strips. Serve immediately.