Brown the ground beef in a large pot over medium heat. Add the diced onion and minced garlic, then cook until the onion softens.
Stir in the chili powder and cumin. Cook for one minute to release the spices.
Add the diced tomatoes, kidney beans, and beef broth. Bring the mixture to a simmer and cook uncovered for 20 minutes, stirring occasionally.
While the chili simmers, preheat the oven to 400°F. In a mixing bowl, combine the cornmeal, flour, baking powder, and salt.
In a separate bowl, whisk the milk, egg, and melted butter. Pour the wet mixture into the dry ingredients and stir until just combined.
Spread the cornbread batter into a greased 8x8 inch pan. Bake for 15 to 18 minutes until the top is lightly golden.
Let the cornbread cool slightly, then use a ghost-shaped cookie cutter to cut out four shapes. Ladle the chili into bowls and place one ghost cornbread piece on top of each serving.