For the pepper relish: Heat the olive oil in a large skillet over medium heat. When the oil is hot, add the Fresno chiles, garlic, jalapenos, bell peppers and onion and sauté for to 4 minutes to soften. Add the vinegar, honey and mustard seeds. Bring to a boil and cook, stirring occasionally, until thickened, about 10 minutes.
For the sandwiches: While the relish cooks, grease a griddle with the butter and place it over medium-high heat. When the griddle is hot, add the sausage pieces cut-side down and cook until well browned and crisp, about 3 minutes. Flip and place 2 pieces of provolone onto each sausage piece. Cook until the cheese has melted completely, another 2 to 3 minutes. Remove to a plate.
Build the sandwiches by spreading the mayonnaise on the bottoms of each bun and laying on a piece of lettuce. Top each with a cheese-covered sausage piece and a generous portion of the pepper relish. Replace the top half of the buns and serve.