Preheat oven to 400 degrees.
Grease 24 miniature muffin cups with a little of the oil.
Using a round 2 1/2-inch to 3-inch round cookie cutter and cut two rounds out of each tortilla.
Lay 1 tortilla round on a smooth, flat surface.
Brush, lightly, with a little more of the oil.
Fit one tortilla round, oiled side up, into each of the prepared muffin cups.
Bake until tortillas are lightly browned and crispy, about 6-8 minutes.
Remove from oven and cool in pan for 10 minutes.
Remove tortilla cups, transfer to a rack and cool completely.
Heat 2 tbsp of oil in a large frying pan set over medium-high heat.
Add onion and garlic; saute until vegetables are very tender, about 6-8 minutes.
Add beef, breaking up with the back of a fork, and cook until beef is brown and cooked through, about 4-6 minutes.
Add chili powder and 2 tbsp cilantro, stirring to blend.
Add beans, corn and tomato sauce.
Cover and cook, stirring occasionally, until mixture is heated through, about 6-8 minutes.
Stir in remaining cilantro, salt and pepper.
Fill each tortilla cup with some of the beef mixture.
Set bowls of sour cream and cheese in the center of a large serving platter.
Arrange tortilla cups around bowls.
Serve immediately.
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