Sautee onion and pepper in about 2 tblsp butter until soft, about 7 minutes, over medium heat, adding the minced garlic in the last 2 minutes of cook time. Be careful not to burn the garlic or it will be bitter.
In a medium mixing bowl, add the bread crumbs, the herbs, the ground chicken and the sautéed vegis. Mix until well combined. Form into 4 patties. Rub the tiniest amount of olive oil on both sides of each pattie, to prevent it from sticking to the grill.
Over medium-low flames, grill the burgers for about 7 to 8 minutes, each side, until no longer pink. Top with Havarti and let melt for a minute. Place the burgers on the buns, top with tomato and mayonnaise.