Place cubed English muffins on a baking sheet. Leave on counter overnight to dry out or toast under the broiler.
Spray an 11 x 7 (2 Quart) deep baking dish with cooking spray. Layer ½ of English muffins on bottom, top with ½ ham and ½ shredded cheese. Repeat, ending with cheese.
In a medium size mixing bowl, whisk together half and half, eggs, salt, pepper, mustard, garlic, onion powder, thyme and nutmeg until fully combined. Pour evenly over the ingredients.
Using the back of a spoon gently press muffin cubes into the custard and make sure it's evenly distributed. Cover with plastic wrap and chill overnight.
To bake: Preheat oven to 350°F Remove from fridge 15 minutes prior to baking. Dot top with butter and sprinkle with paprika.
Remove plastic wrap and cover with foil. Bake covered for 30 minutes, then uncover and continue to bake for another 15-20 minutes until top is golden and a knife inserted into the center comes back clean.
Meanwhile, make hollandaise sauce. See step-by-step instructions here.
Let stand 5 minutes on counter. Drizzle with hollandaise just before serving with additional on the side, if desired. Garnish with chives or parsley.