In a large mixing bowl, combine the pork, red onion, rosemary, thyme, chilli powder (if using) and crumbled Stilton. Season with black pepper, then form into 4 burgers. Keep covered and chilled.
When ready to cook, preheat the grill, barbecue or char-grill pan. Cook the burgers for 8-10 minutes per side, depending on their thickness (they should be thoroughly cooked).
Split the burger buns and toast the cut sides, if you like. Top with salad leaves, then a burger. Finish each one off with a slice of Stilton and a drizzle of sweet chilli sauce, if you like.
For a great mini treat for parties and buffets, form the burgers into meatballs and bake in the oven at 200°C/fan oven 180°C/Gas Mark 6 for 20 minutes, then serve in warm pitta breads with salad and sweet chilli sauce.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.