For the spinach, in sauté pan over medium heat, melt butter. Add garlic and onion, and cook until soft. Add spinach and sauté until soft. Add heavy cream and nutmeg. Cook until slightly reduced and thickened, but still liquidly. Remove from heat; fold in cream cheese. Set aside and allow spinach to cool completely.
Preheat oven to 325ºF.
Spread bread cubes on a baking pan and bake until golden brown, stirring occasionally, about 25 minutes. Remove and let cool. Once cooled, place in a mixing bowl.