Pulled Pork Tamale Pie

Name: Pulled Pork Tamale Pie
Ingredients: 1.5 teaspoons butter, or as needed; 2 tablespoons vegetable oil; 1 small onion, minced; 2 cloves garlic, minced; 2.5 cups prepared pulled pork; 1 (15.25 ounce) can whole kernel corn; 1 (10 ounce) can diced tomatoes and green chiles (such as RO*TEL®); 1 (4.5 ounce) can diced green chiles; 1 (1.25 ounce) package taco seasoning; 2 (6 ounce) boxes cornbread mix (such as Martha White®); 1.3333333730698 cups milk; 2 large eggs; 1 (8 ounce) package shredded Mexican-blend cheese