Preheat the oven to 350°.
Grease a 9x13 pan and set aside.
Dice bread into 1 1⁄2 inch cubes.
Slice Canadian bacon into quarters.
In a large bowl, whisk eggs, milk, heavy cream, green onions, salt, pepper, garlic powder, and Dijon mustard together.
Add the bread to the casserole dish.
Next, sprinkle the cheese and Canadian bacon over the bread.
Pour the egg mixture over the top, covering all the bread.
Gently push down any pieces of bread that weren't covered and gently press in cheese.
Dice butter into small cubes and randomly place over the top.
Bake uncovered for 55-60 minutes or until set.