Preheat the oven to 375F.
Cut the bread and SPAM into half-inch cubes.
Place the milk and cream cheese in a bowl. Heat on HIGH in the microwave for a minute and a half. Beat lightly to bread up the cream cheese.
Place the bread in a large bowl. Pour in the cream cheese and milk mixture. Add the eggs, mustard, paprika and garlic. Stir to combine. Add the SPAM cubes. Stir.
Butter the bottom and sides of a baking dish (mine is 13" x 9").
Pour in the bread and SPAM mixture. Smoothen the surface to spread evenly.
Spread the grated cheese over the entire surface.
Bake for about 30 minutes or until slightly risen, fluffy and the top is nicely browned with toasted spots.
Rest for about five minutes before cutting into squares or rectangles.
Serve the cheesy SPAM bake warm.