Preheat the oven to 220C, fan-forced. Line an oven tray with baking paper. Remove 20g butter from the fridge to soften. Halve the unpeeled sweet potato crosswise, then cut into very thin wedges. Put on the lined tray, drizzle with 2 tsp olive oil, season with salt and pepper and toss to coat. Roast for 15 mins or until tender.
Step 2 — Prep ingredients
Meanwhile, trim the lettuce, then shred. Finely chop the celery. Finely chop the dill, including the stems. Finely grate the zest of half the lemon*, then juice the half.
Step 3 — Make dill-lemon mayo
Put the aioli, celery, lemon zest, half the dill and 2 tsp lemon juice* in a bowl, season with salt and pepper and stir to combine.
Step 4 — Bake bread rolls
Split the bread rolls through the middle. Put on an oven tray, cut-side up, and bake for 5-6 mins until lightly toasted. Spread the cut sides with the butter.
Step 5 — Cook prawns
Heat 2 tsp olive oil in a medium frypan over high heat. Add the prawns, season with salt and pepper and cook, stirring, for 2-3 mins until just cooked through.
Step 6 — Get ready to serve
Add the prawns to the dill-lemon mayo and stir to combine. Taste, then season with salt and pepper. Divide the lettuce and prawn mixture among the bread rolls and scatter with the remaining dill. Serve with the sweet potato wedges.