Preheat oven to 160 degrees.
Place a medium sized frypan over medium-high heat.
Add butter, onion and garlic and gently saute until translucent. Stir through macadamia nuts and breadcrumbs and continue to cook for 2-3 minutes.
Remove frypan from heat.
Add mustard, lemon juice, lemon zest, parmesan cheese and mint. Mix together well. Season to taste with salt and pepper. Set aside to cool.
Place a large piece of cling wrap onto a clean, flat surface. Arrange fillets of skirt steak on top of the cling wrap to make a rectangular shape.
Using your hands, firmly press fillets into each other, ensuring that there are no gaps.
Evenly spread mint and macadamia stuffing over the surface area of the meat.
Using cling wrap, as a rolling aid, gently life the edge of the meat closest to you.
Roll the lamb into a roulade, pulling the cling wrap away as you go. Truss the roulade with kitchen string at 2-3cm intervals to ensure it stays together while cooking. Season with salt and pepper.
Add grapeseed oil to a medium-sized frypan and place over medium-high heat.
Add roulade to the pan and brown on all sides.
Place roulade in the oven to cook for 1-1.5 hours or until meat is tender. Remove from oven and allow to rest for 10-15 minutes.
To serve, place feta and yoghurt into a food processor and blend until smooth. Add generous spoonfuls of feta sauce to each plate.
Using a sharp knife, cut roulade into portions, remove string and place on top of sauce.
Garnish with mint, serve and enjoy, preferably along side a fresh, green salad and crusty bread.