Preheat the oven to 375F. Pour 1 cup of boiling water over the cashews and let sit for 30 minutes while you prepare the rest of the ingredients.
In a large dutch oven, heat the olive oil over medium heat until shimmering. Add the shallots, mushrooms, garlic, and a pinch of salt and pepper. Cook until softened, about 7-9 minutes. Sprinkle the flour over the mushroom mixture and cook for 2-3 minutes.
While whisking constantly, slowly pour in 2 1/2 cups of the chicken stock. Bring to a simmer and cook for about 5 minutes, until thickened.
Meanwhile, drain and rinse the cashews. Place them in a high-speed blender with 1 cup of chicken stock. Blend until completely smooth. Add the cashews to the sauce mixture along with the soy sauce and hot sauce. Remove from the heat.
Stir the brown rice, chicken, broccoli (and dairy-free cheese if using) into the sauce. Taste and season with additional salt if needed and plenty of black pepper. Add up to 1/2 cup additional chicken stock if the mixture looks too thick. Pour into a greased 3-quart casserole dish. Combine the bread crumbs and butter and sprinkle over the top.
Bake for 25-30 minutes until bubbly and golden on top. Enjoy!