This needs to be prepared a few days beforehand.
Combine the vinegar and sugar in a saucepan and stir over high heat until sugar dissolves.
Bring to the boil, then reduce to a simmer and cook for 20 mins, uncovered and without stirring. It will reduce and become syrupy. Allow to cool and then refrigerate overnight.
On the same day, peel and cut the beetroot. Place in a bowl and combine well with the salt, cover and refrigerate overnight.
On the next day drain any liquid from the beets and place in an airtight jar and cover with the pickling liquid.
Slice the ginger and add to the jar.
Heat the taco shells in the oven as per packet instructions.
Thinly slice the lettuce, avocado and cucumber.
Place a frypan with a little oil over high heat and grill the corn kernels for 2-3 mins, until lightly golden. I used frozen kernels, but if corn is in season slice the kernels off a fresh cob.
Then it's just a matter of assembling your tacos with lettuce, beef, grated cheese, corn, avocado and cucumber.
The pickled beetroot will keep for 2 weeks in the fridge.