Peel the king prawns and cut into cubes, taking care they don’t come apart.
Mix the juice of half a small lime, the soya sauce, the extra-virgin olive oil and the ground ginger in a bowl. Taste to see whether you need to add any extra salt. Add the cubed king prawns and leave to marinate for at least half an hour.
In a separate bowl, mix together the avocado, a dash of lime juice and a little extra-virgin olive oil.
Remove the avocado and the king prawns from their bowls and assemble the tartare with the help of a metal ring: first a layer of king prawns, then a layer of avocado. Top off with a scattering of sesame seeds.