In a small bowl, combine tamari, sugar, ginger and cayenne. Set aside.
In a large nonstick skillet on medium, heat oil. Add garlic and cook for 30 seconds. Stir in mushrooms and cook for 3 to 4 minutes more, stirring occasionally. Mix in cashews and half of green onions, then add tamari mixture and stir well. Cook, stirring constantly, until excess liquid has evaporated, 1 to 2 minutes.
To serve, scoop mushroom filling into the center of lettuce leaves. Drizzle with sriracha, and sprinkle with remaining half of green onions and a squeeze of lime.
Blending cashews with lemon juice and hot water creates a luscious cream for this plant-based take on comforting stroganoff. Mushrooms are full of umami taste, which gives the sauce full-bodied flavor in a fraction of the time it takes to make the original beef version.
Portobello mushrooms have a meaty texture that makes them a stellar swap for beef patties in veggie burgers. But here's the trick: We've actually used the mushroom caps as the bun, then filled the middle with warmed marinara sauce, provolone and fresh, crisp greens.