Add oil and onion to a medium sized saucepan. Cook over medium-high heat until onion starts to caramelize. Stir in garlic, chili powder and corn flour. Stir for about 45 seconds until fragrant.
Slowly stir in water to prevent lumps. Add remaining ingredients and stir until well combined.
Simmer over low heat while making steak filling.
In a large skillet, heat butter and oil over high heat until hot. Add steak in a single layer and cook until steak starts to brown. Flip steak over and add onions, bell peppers and jalapeño if using. Cook until onion is softened.
Stir in 3/4 cup enchilada sauce. Remove from heat to prevent over cooking the steak.
Preheat oven to 400 degrees.
In a large oven safe baking dish place a thin layer of enchilada sauce and set aside.
Lay tortillas on a work surface. Spread with a heaping spoonful of refried beans. Top with 2 spoonful of steak filling. Cover with 2 tablespoons cheese mix.
Tuck sides in and roll like a burrito. Place seam side down in enchilada sauce in baking dish.
Cover the center of each rolled burrito with a strip of enchilada sauce and cover with remaining cheese.
Bake uncovered for 15-20 minutes until cheese is melted and burritos are hot. Garnish with desired condiments or serve on the side.