2 tablespoons unsalted butter
4 tablespoons vegetable oil
1 white onion, chopped
3 cloves garlic, chopped
1 jalapeno pepper, diced (remove seeds for less heat)
1 1/2 teaspoons chili powder
1/2 teaspoon ground cumin
1/4 teaspoon ground cinnamon
1 small tomato, chopped, plus more for topping
2 tablespoons chopped fresh cilantro
2 1/2 cups shredded chicken
1/4 cup sour cream
1 15 -ounce can refried beans
4 10 -inch flour tortillas
1 cup shredded monterey jack cheese, plus more for topping
Heat 2 tablespoons oil in the skillet. Add the onion, garlic and jalapeno and cook until soft, about 3 minutes. Add the chili powder, cumin, cinnamon and 1 teaspoon salt; toast 30 seconds. Add the tomato and cilantro and cook until slightly dry, about 2 minutes. Stir in the chicken and sour cream and warm through. Remove from the heat.
Preheat the oven to 450 degrees F. Melt the butter with 2 tablespoons vegetable oil in a skillet; transfer to a bowl. Brush a rimmed baking sheet with some of the butter-oil mixture. Spread 2 tablespoons refried beans down the center of each tortilla, leaving a 2-inch border on both ends. Top with 1 cup chicken mixture and 1/4 cup cheese. Fold in the ends and roll up.
Put the chimichangas seam-side down on the baking sheet; brush with the butter-oil mixture. Bake 8 to 10 minutes per side, brushing again after you flip. Serve with cheese, tomato and avocados.