Mix sauce ingredients in a bowl: mayonnaise, Mexican crema, tajín, 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 olive oil, if needed. Add corn kernels, diced 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 cooked rice into a bowl. Top with chicken, a big scoop of street corn, and garnish with avocado, cotija cheese, and cilantro. Serve with a lime wedge and extra sauce drizzled on top if desired.