Mix the uncooked corn kernels, milk, masa, salt, and pepper in a saucepan and cook over medium-low heat for 10-15 minutes. Remove from heat and cool slightly. Add the diced peppers, cilantro, scallions, and roasted corn kernels, and mix well. Combine the butter and baking soda and fold into the batter. Form the mixture into 5-inch pancakes. Cook on a lightly greased griddle at medium heat until golden brown on both sides. Sauté the onion and chicken for a few minutes until heated, then add the barbecue sauce. Put a pancake on each plate. Top with 2 tablespoons of avocado or guacamole and 3 heaping tablespoons of the chicken mixture. Garnish with sour cream and cilantro sprigs. Serves 4-6.