Pre-heat a conventional oven to 350°F.
Place 4 tortillas on a cookie sheet and bake for 10-12 minutes, or until crisp, flipping over half way through cooking.
Meanwhile, smash white beans with a potato smasher, and combine with olive oil, adjust oil to desired creaminess of the beans. Warm the smashed beans in a pre-heated sauté pan, over medium heat. Reserve warm.
Once the tortillas are crisp, on each tortilla spread 3 tbsp. of white beans over the crisp tortilla, sprinkle with ¼ cup ground turkey, ½ cup romaine lettuce, 2 tbsp. queso fresco, 1 tbsp. yellow corn, 1 tbsp. red onion, and sprinkle with cilantro.
To serve: serve each tostada with a lime wedge to be squeezed over.