Into a large deep skillet over medium-high heat, add vegan butter. When the butter is melted, add chopped mushrooms and onion.
Cook, stirring frequently for 2 minutes, until softened and fragrant.
Add garlic and rice then continue cooking an additional 1 minute.
Stir in vegan chicken-style broth, tamari, toasted sesame seed oil, and ground black pepper.
Bring to a boil then reduce heat to low.
Cover and simmer for 20 minutes, until liquid is absorbed and rice is tender.
Using a fork, gently fluff the rice. Garnish with sliced scallion.