Put the beef into a medium mixing bowl and generously season with salt and pepper. Heat the oil in a small skillet over medium heat; add the shallot and garlic and cook, stirring, until translucent, about 4 minutes. Remove from the heat and cool.
Meanwhile, mix together the egg, panko, Worcestershire and oregano in a medium bowl, and stir until combined. Add the breadcrumb mixture to the beef, along with the cooled shallots and garlic, and mix until the ingredients are well combined. Using a 1/2-cup measure, divide the mixture into 6 equal portions and form them into long ovals, about 1/2-inch thick. (If using the mixture to make Mini Meatball-Stuffed Pitas, recipe below, reserve 1 cup of the seasoned meat and make only 4 burgers.)
Preheat the broiler and position a rack 8 to 10 inches below it. Heat a heavy grill pan or griddle over medium-high heat. Cook the burgers, turning once, until cooked through, about 5 minutes per side.
Meanwhile, spread a thin layer of Chipotle Aioli on the cut sides of the rolls and put them on a baking sheet, cut-sides up. Broil until the aioli browns slightly and the rolls are toasted on the edges.
To assemble the burgers, place a burger on each roll and top with lettuce, avocado, jalapeno and more aioli, if desired. Serve immediately.
Put the garlic and chipotle in a food processor and puree until very smooth. Add the mayonnaise and lime juice and blend until smooth; season with salt and pepper. Store in an airtight container for up to 1 week.
Preheat the oven to 350 degrees F. Spray a baking sheet with cooking spray. Roll the meat mixture into16 mini meatballs, about 1 inch in diameter and place them on the baking sheet. Bake until completely cooked through, about 12 minutes. Cool briefly.
To assemble, cut the top third off of each pita. Divide the meatballs among the pitas, top with lettuce, cucumbers and tomatoes and drizzle with the sour cream. Yield: 4 pitas