Mix all the ingredients together in a small bowl. Add freshly ground black pepper then place on a piece of baking paper and roll up into a cigar shape, twisting the ends. Place in the freezer to firm up quickly.
Preheat the barbecue plate, grill or frying pan to a medium heat. Place the onion, garlic, bread with milk, egg, Dijon mustard and Parmesan cheese (if using), in a large bowl and mix well to break up the bread or mix in a food processor. Add the beef mince and season. Mix to combine.
Using wet hands mix together forming into 8 patties about 2.5cm thick, pressing together just enough to form loose but shaped patties. Make a horizontal slit in the side of each patty and place in a small slice of the bistro butter.
Place the patties onto a well heated oiled barbecue plate or pan. Cook for about 5 minutes on each side before transferring to a warm plate.Cover loosely with foil and leave to rest while you grill the vegetables.
Place prepared vegetables in a large bowl and toss with oil and lightly season. Cook on the barbecue, grill or frying pan for about 3 minutes on each side until tender.
Stack the ingredients by placing one patty on a plate and spread with a little hummus. Place on some grilled vegetables then top with another patty. Finish with a few more grilled vegetables. Repeat with remaining patties and vegetables. Serve with a simple green leaf salad dressed with vinaigrette.
Recipe from recipes.co.nz