Position rack in center of oven and preheat the oven to 375ºF.
To make the tortilla "bowls", cut a 3-inch wedge from each tortilla and discard. Line a baking sheet with parchment paper. Turn a stainless-steel mixing bowl upside down and place it on the parchment paper. Brush each side of the tortilla with 1 teaspoon of the olive oil. Drape each tortilla over the bowl (you will be able to do only one at a time), placing the cut ends together so that they now resemble an upside down shallow cone. Bake until crisp, about 10 minutes (tortilla will get crisper as it cools). Hint: If you have more than one small ovenproof bowl, you may be able to bake more than one tortilla at a time.
Using oven mitts or pot holders, remove the baking sheet from the oven and carefully transfer the crisp tortilla "bowl" to a wire rack to cool. Repeat with the remaining tortillas, Set aside.
While the tortilla "bowls" are baking, set the skillet over medium heat. Add the ground beef and cook, stirring occasionally, until brown, about 5 minutes.
Remove from the heat and strain the beef in a colander set over a bowl to remove the fat. Discard the fat and return the beef to the pan and add the onion. Cook, stirring occasionally, until the onions are soft, about 3 minutes.
Add the tomato paste and garlic, stir to blend, and cook for about 30 seconds. Add the chili powder, Baby Bam, and salt. Stir to blend and add the chicken broth.
After about a minute, when the broth is reduced by half, remove from the heat and set aside to cool.
To assemble the salads, place a tortilla "bowl" right side up onto each of 4 plates. Place 1/2 cup of the ground beef mixture in the center of each tortilla "bowl." Top with 1/2 cup of the shredded lettuce, 1/3 cup of the tomatoes, 2 tablespoons of the cheese, and 1 tablespoon of the sour cream. Serve immediately, with Salsa and Guacamole, if desired.
YIELD: 4 servings