Preheat oven to 400 degrees. Lightly grease mini muffin pan compartments with cooking spray.
Heat oil to a shimmer in a medium-sized skillet over medium heat. Add burger meat and onion. Season with salt and pepper if desired. Fry burger meat, stirring occasionaly to prevent sticking, until thoroughly cooked, about 10 minutes. Remove rom heat.
In a medium sized bowl, mix together baking mix, milk and egg into a soft batter.
Spoon 1 tablespoon biscuit mix into each prepared pan cup. Add 1 tablespoon ground meat mixture. Top with pickle slice then shredded cheese.
Bake at 400 degrees for approximately 10 minutes until lghtly browned and inserted knife comes out clean. Cool slightly in pan before removing cheeseburger pie bites to finish cooling on cooling rack. Serve at room temperature or reheat for several seconds in the microwave.