For Crust: Heat oil in a heavy non-stick skillet over medium heat. Working in batches, add plantain slices and cook until golden brown, about 3 minutes per side. Using slotted spoon, transfer slices to sheet of foil. Pat plantains with paper towels and cool Reserve 2 tbsp of oil from skillet for the filling.
Line a 9-inch glass pie dish with a single layer of cooled plantains. Reserve remaining for garnish. Using fingers, firmly press slices together to seal any gaps. Set crust aside.
For Filling: Heat reserved 2 tbsp of oil in large non-stick skillet over medium-high heat. Add onion and garlic and sauté until onion is translucent, about 4 minutes. Add beef and sauté until brown, breaking into small pieces with back of fork, about 5 minutes.
Add tomato paste, raisins, green olives, oregano, cinnamon, cumin, and allspice. Simmer stirring occasionally (about 10 minutes) until most liquid evaporates and filling is thick. Season to tasted with salt and pepper. Mix in cornmeal.
Preheat oven to 450°F Crumble half of queso fresco over crust, then spoon in picadillo filling and press to compact. Sprinkle evenly with remaining queso fresco.
Bake pie until cheese is melted and filling is heated through, about 25 minutes. Garnish center of pie with sliced olives and some plantain slices. Cool 10 minutes and serve.
Note: Queso fresco, also known as queso blanco, is available at some supermarkets and Latin markets. A mild feta cheese can be substituted.