Add turkey and onion to a large skillet over medium high heat. Cook, stirring frequently, until meat is browned and onions are soft, about 5 minutes. Add taco seasoning following package directions. Reduce heat and simmer for 10 minutes.

To make the tacos, spread about 1 Tablespoon of refried beans on half of a corn tortilla. On the other half, place a heaping spoonful of turkey mixture, and sprinkle with shredded cheese. DO NOT FOLD the tortilla in half at this time or the tortilla will crack.

Heat a large skillet over medium heat. Add enough vegetable oil to coat the bottom of the pan. When the oil is hot, place the prepared tortilla flat into the pan. Allow to cook for about 30 seconds until the tortilla becomes pliable. Using tongs, carefully fold the tortilla in half.

Continue to cook for 2-4 minutes per side, until tacos are golden and crispy. Remove from pan and drain on a paper towel. Repeat with remaining tortillas, adding additional vegetable oil to the pan as necessary.

While the tacos are still warm, carefully open each one and stuff with optional fillings.