Preheat the oven to 325 degrees.
Place the broccoli florets in a microwave safe bowl with a lid. Add water, cover and microwave on high for 2 1/2 minutes to steam, until broccoli is barely soft. Do not overcook.
In a medium skillet over medium high heat, sauté the onions and garlic in the olive oil until onions are soft. Reduce heat and stir in flour, stirring constantly.
Mix in soy milk and vegetable broth, continuing to stir constantly, until sauce has thickened. Remove from the stove and stir in nutritional yeast, butter, nutmeg, mustard powder, and salt.
In a large bowl, combine sauce, steamed broccoli and cooked rice and mix well. Transfer to into a large casserole or baking dish. Spread the top with the bread crumbs.
Cover and place in the oven. Bake for 25 minutes, remove the lid and bake for an additional 10 minutes.