Before starting, preheat the oven to 450°F. Wash and dry all produce. Strip rosemary leaves from stems, then finely chop 1 tsp (dbl for 4 ppl). Cut potatoes into 1/2-inch wedges. Add potatoes, rosemary and 1 tbsp oil (dbl for 4 ppl) to a parchment-lined baking sheet. Season with salt and pepper, then toss to coat. (NOTE: For 4 ppl, use 2 baking sheets, with 1 tbsp oil per sheet.) Roast in the middle of the oven until golden-brown, 25-28 min. (NOTE: For 4 ppl, roast in the middle and the bottom of the oven, rotating sheets halfway through.)

While potatoes roast, cut tomato into 1/4-inch slices. Cut halloumi into 1/4-inch slices. Rinse halloumi in cold water, then pat dry with paper towels. Stir together basil pesto and mayo in a small bowl. Set aside.

Heat a large non-stick pan over medium-high heat. When hot, add halloumi to the dry pan. Cook until golden-brown, 1-2 min per side. (NOTE: Don't overcrowd the pan. Cook in batches for 4 ppl.)

While halloumi cooks, halve buns, then arrange them on another baking sheet, cut-side up. Toast in the top of the oven until golden-brown, 3-4 min. (TIP: Keep your eye on them so they don't burn!)

Spread basil aioli over buns. Top bottom buns with spring mix, halloumi and tomatoes. Divide buns and potato wedges between plates.