Check your avocado is ripe before starting this recipe (see Kitchen notes). Preheat the oven to 220C, fan-forced. Line an oven tray with baking paper. Cut the unpeeled potatoes into 1cm-thick fries. Put the potato on the lined tray, drizzle with 2 tsp vegetable oil, season with salt and pepper and toss to coat. Bake on the upper oven shelf for 25-30 mins until golden and tender.
Step 2 — Prep fillings
Meanwhile, thinly slice the cucumber. Thinly slice the avocado. Trim the lettuce, then separate the leaves.
Step 3 — Prep smoked salmon
Separate the smoked salmon slices, then coarsely tear into pieces. Combine the sriracha sauce (see Kitchen notes) and 2 tsp mayonnaise in a large bowl. Add the smoked salmon and toss to coat.
Step 4 — Toast buns
Halve the buns. Once the fries have been baking for 20 mins, put the buns on an oven tray, cut-side up, and bake on the lower shelf for 5 mins or until lightly toasted.
Step 5 — Serve up
Spread the buns with the tonkatsu sauce. Top with the sriracha smoked salmon, seaweed, cucumber, avocado and lettuce, then sandwich with the bun tops. Serve the sushi burgers with the fries, remaining lettuce and remaining seaweed. Enjoy!
Step 6 — Kitchen notes
To speed up the ripening process, put the avocado in a paper bag and loosely close, then leave on the kitchen bench for a day or two. Add a banana to the bag to make the avocado ripen faster. ~ Sriracha is a Thai hot chilli sauce. If you prefer less heat, reduce the sriracha to taste.