Blanch green beans in salted boiling water for 3–4 minutes, then transfer to an ice bath. Drain and set aside.
Heat oil in a medium saucepan over medium heat.
Add shallot, garlic, and ginger; sauté until fragrant.
Stir in green curry paste and cook 30 seconds to bloom flavor.
Pour in coconut milk, soy sauce, maple syrup, and nutritional yeast.
Simmer 5–6 minutes until thickened slightly, stirring often.
Add lime juice and zest; season with salt and pepper.
Combine green beans (and mushrooms if using) with the sauce in a large bowl. Transfer to baking dish.
In a skillet, toast panko, coconut, and cashews with oil until golden. Stir in parsley and a pinch of salt.
Sprinkle topping over the casserole and bake at 375°F (190°C) for 15–20 minutes, until bubbling and golden.
Garnish with lime zest, basil, and chili slices. Serve warm.