Place your broccoli in a steamer basket set over boiling water and cover. Cook until it just begins to tenderize and is bright green, about 5 mins. Transfer to a large bowl.
Heat the oil in a medium pan on medium high heat. Cook the onion and garlic until golden brown, about 5 minutes
In a small pot, whisk 3/4 cup of the almond milk with paprika, mustard, salt and nutmeg. Bring to a boil. Additionally, whisk the cornstarch with the remaining 2 Tbsp of milk in a small bowl.
Once the milk is boiling, whisk in the cornstarch mixture, stirring constantly. Boil until thickened and coats the back of a spoon, about 2-3 minutes. Stir in the onion mixture.
Pour the sauce over the broccoli and stir to coat, then stir in the cheese. Transfer to a casserole dish
Wipe and dry your pan and heat to medium high. Toast the panko until golden brown, about 2-3 minutes and sprinkle on the casserole