Cook the Angel Bay Premium Angus Beef Patties according to instructions on the packet.
While patties cook, heat oil in a small frying pan on medium heat. Add garlic and rosemary and gently sizzle for 2 minutes, without browning the garlic. Transfer to a small bowl and leave to cool completely.
Return pan to heat and add 1 1/2 tablespoons butter. Once melted, add onion, vinegar and sugar. Cook, stirring occasionally, until onions are soft and caramelised (10-15 minutes).
Meanwhile, melt remaining tablespoon of butter in a separate medium frying pan on medium heat. Add mushrooms and cook, stirring occasionally, until browned and tender. Push to one side of the pan, then add capsicum to warm through.
Season onions and mushrooms with salt and pepper. Stir mayonnaise into the rosemary olive oil mixture.
Slice burger buns in half and lightly toast or grill. Top the bottom halves of the buns with a
slice of cheese, onions, red peppers, burger patty, more cheese, mushrooms and rocket.
Spread the top halves of the buns with rosemary mayonnaise before sandwiching