Preheat the oven to 220C, fan-forced. Thinly slice the cucumber. Combine 2 tsp white wine vinegar and 1 tsp sugar in a large bowl. Add the cucumber and toss to coat. Set aside to pickle, tossing occasionally, until needed.
Step 2 — Make batter
Combine the cornflour, 2 tbs plain flour and 3 tsp pepper and garlic seasoning (see Kitchen notes) in a large bowl and season with salt. Add 2½ tbs water and whisk until smooth. (The batter should be smooth and pourable, but thick enough to coat the back of the spoon. If yours is too thick, whisk in 1 tsp water at a time until it reaches the desired consistency.)
Step 3 — Fry hotdogs
Heat 1cm vegetable oil in a medium deep frypan over medium-high heat until the oil is shimmering. Using tongs, dip the sausages into the batter to coat, then carefully add to the hot oil. Cook, turning occasionally, for 4-5 mins until golden and cooked through. Drain on paper towel.
Step 4 — Toast rolls
Meanwhile, halve the bread rolls down the middle, being careful not to cut all the way through. Put on an oven tray and bake for 4 mins or until lightly toasted. Remove from the oven and cover with a clean tea towel (see Kitchen notes).
Step 5 — Serve up
Drain the cucumber, reserving the pickling liquid. Combine the reserved pickling liquid and 2 tsp olive oil in a large bowl and season with salt and pepper. Add the salad leaves and toss to coat. Fill the rolls with the sausages and cucumber pickles, then drizzle with the smoky aioli. Divide the hotdogs and salad among plates and enjoy!
Step 6 — Kitchen notes
Our pepper and garlic seasoning has a mild peppery kick, so reduce the amount if you prefer less heat. ~ Covering the rolls with a tea towel after toasting allows them to steam a little, which softens the crust.