Grease a 6-cup souffle dish.
Layer the bread and cheese in the prepared souffle dish, ending with a layer of cheese.
Combine the eggs, melted butter, milk and powdered mustard in a food processor and spread the mixture over the bread and cheese. Cover and refrierate for a least 8 hours, or overnight
Preheat the oven to 350 and bake for 60 minutes or until puffed up and golden.
Cutr into wedges and serve immediately.
For variety, add cooked shrimp, ham or bacon to the bread and cheese layers.