Brown the beef and pancetta in the oil in a large skillet until golden brown, about 5 minutes. Stir in the garlic, carrots
, celery, onions
and bell peppers
and sprinkle with salt and black pepper. Add the tomatoes
, cheese, ketchup, paprika, sugar, vinegar, Worcestershire, cayenne, thyme and jalapeno and bring to a boil. Reduce the heat to a simmer
and cook, covered, 15 minutes. Taste and adjust the seasoning, and then stir in chives
Toast the buns in a grill pan
. Divide the beef between the buns on 4 plates and garnish with shaved cheese.