Slice the top off each pepper just below the base of the stems and discard; carefully scoop out seeds and membranes.
Bake on foil-lined cookie sheet at 350 degrees for 15 minutes to soften.
Heat olive oil in a skillet on medium-high heat and add beef, browning. When the beef is no longer pink, push to the side and turn heat to low. Sautee shallots on the other side of the skillet for 2-3 minutes.
Add tomato paste, vinegar, sugar, garlic powder, onion salt, Worcestershire, mustard, paprika, salt and pepper. Pour chicken stock over mixture and stir well to incorporate; let simmer, covered on low heat, for at least 5 minutes.
Fill peppers with Sloppy Joe mixture. Cover each with cheese and return to the oven at 350 degrees for 10 minutes, until the cheese is melted. We like to top ours with pickled jalapenos and hot sauce!