Mix sauce ingredients in a bowl: mayo, sour cream, tajin, lime and milk. Set aside.
Season chicken breasts on both sides with salt, pepper, chili powder, cumin, paprika, garlic powder and oregano. Heat a skillet over medium heat. Add olive oil and once hot, add chicken and cook until cooked through (165 degrees), flipping once. Remove to a plate.
To the same skillet add a little more oil, if needed. Add corn and onion and jalapeño. Turn heat to high, cover with lid and sauté, stirring occasionally, until corn is charred and tender, about 4-5 minutes. Remove from heat. Stir in half of the sauce, to make a creamy street corn mixture.
Spoon rice into a bowl. Top with chicken, a big scoop of street corn and garnish with avocado, cheese and cilantro. Serve with a lime wedge and extra sauce drizzled on top, if desired.
