Spread butter onto one side of each slice of bread. Cut into quarters. Lay half of the bread, butter side down, in the bottom of a 9x13 inch baking dish. Top with half of the Cheddar cheese and half of the Monterey Jack. Layer the remaining bread over the cheese, and top with the other halves of the cheeses.
In a large bowl, whisk together the eggs, half-and-half, and milk. Stir in the brown sugar, salt, pepper, cayenne, onion powder, mustard powder, and Worcestershire sauce. Pour over the cheese and bread. Cover, and refrigerate at least 6 hours, preferably overnight.
Preheat the oven to 325 degrees F (165 degrees C). Bake the strata uncovered for 1 hour in the preheated oven. Let stand for 10 minutes before serving. Slice and garnish with fresh parsley.