In a medium saucepan, combine broth and 1 can of water and bring to a boil over medium-high heat. Add chicken, reduce to a simmer, and cook for 12 minutes. Remove from heat and let cool in poaching liquid, 15 to 30 minutes. Shred chicken using two forks.
Preheat the oven to 400°F. In a large bowl, combine chicken, salsa, cumin, oregano, cheese, and scallions. Divide the mixture into 6 portions. Place 1 portion filling in center of a tortilla; fold left and right Side dish of tortilla over filling, then fold tops and bottoms over Side dish to form square, securing with toothpick if necessary. Repeat for remaining tortillas.
Place each chimichanga seam-side down on a baking sheet and brush with olive oil. Bake for 25 minutes, or until golden brown. Garnish with scallions, salsa, sour cream, and lettuce.