Preheat the oven to 375 degrees F. Grease a baking dish with cooking spray and set aside.
Steam the cauliflower florets until tender, about 10 - 15 minutes. When done, remove from pot, transfer to a blender and add the cashews, 1/4 cup of almond milk, mustard and spices. Blend until smooth, adding more almond milk 1 tablespoon at a time until the texture resembles a very thick soup. Set aside.
Place quinoa in a large mixing bowl. Pour sauce over quinoa, add 1 cup of cheese stir to combine. Fold in rosemary, reserving a tablespoon for sprinkling on top.
Transfer mixture to prepared baking dish. Sprinkle with remaining cheese and rosemary, and bake for 20 - 30 minutes until cheese has started to brown and the filling is bubbly.
Remove from oven, let cool for 5 minutes and serve.
If you're freezing, you can either freeze before baking (just let defrost night prior and increase baking time slightly) or freezing after baking and just reheating when ready to eat.