Preheat oven to 375°F (190°C)
Pound chicken breasts to even thickness
Season chicken with salt, pepper, and nutmeg
Heat a skillet over medium heat and cook chicken until lightly browned and cooked through
Remove chicken from skillet and let it cool slightly before slicing into strips or cubes
In a mixing bowl, combine cream cheese, shredded cheddar, garlic, and milk
Add spinach and mix until evenly distributed
Add cooked chicken to the mixture and stir
Transfer the mixture to a baking dish and spread evenly
Top with additional shredded cheese if desired
Bake for 20-25 minutes, until bubbly and golden on top
Serve warm