Preheat oven to 350 degrees F. Grease a 12 hole standard muffin pan and set aside.
Place the beef and the cubes of chicken into a large skillet. Sauté over medium high heat while stirring often until the chicken is cooked through and no longer pink.
Place the cooked beef mixture into a blender. Add the rest of the ingredients and puree until smooth.
Divide the mixture into the prepared muffin pan and bake in the oven for 16-22 minutes or until the muffins are cooked through. Remove from the oven and allow the muffins to cool in the pan before removing. NOTE: if you underbake them, they will shrink.
Store extras in an airtight container in the fridge for up to 4 days. Can be frozen for up to a month.