Grilled Frog Legs Tostadas

Name: Grilled Frog Legs Tostadas
Cuisine: Mexican, Latin American
Ingredients: 12 to 16 frog legs, cleaned; Coarse salt (sea or kosher); Freshly ground black pepper; 2 to 3 cloves garlic, peeled and minced; Extra virgin olive oil; Juice of a lime; For the scallion butter; 1/2 cup butter; 1 scallion, white and green parts thinly sliced; 2 large red ripe tomatoes, diced; 1 to 2 serrano chiles, seeded and finely diced; 1/4 to 1/2 preserved lemon, finely diced (peel and flesh), or to taste; 3 ounces kasseri or feta cheese, diced; 2 tablespoons chopped fresh mint; 12 kalamata olives; Lime juice, to taste; 3 ripe avocados, halved lengthwise and pitted; Sliced scallions; Corn tortillas; Korean gochujang; Lime wedges