Prawn Tacos a la Mexicana

Method

1. Peel the prawns if they still have their shells on, pull the dark thread out of the back of each one and lay them on a plate.
2. Dice the tomato and the onion small, keeping them in separate piles, cut the jalapeno into thin rings and chop the coriander.
3. Warm the olive oil in a wide pan over a medium flame and cook the onion and jalapeno for three minutes, moving them about, until the onion turns glassy at the edges without browning.
4. Add the tomato and lift the heat a little. Press the pieces flat against the base of the pan as they soften, six minutes, until the watery juice has cooked away and what is left is thick and rough enough to hold the mark of a spoon.
5. While the tomato is reducing, put the corn tortillas one after another onto a second dry pan and move them into a covered dish as they come off, where the trapped steam holds them soft.
6. Slide the prawns into the sauce and turn them through it for three minutes, until every one has curled and gone opaque right to the middle. Squeeze in the half lime off the heat.
7. Put the pan of prawns and the covered tortillas in the middle of the table and scatter the coriander over the top. Spoon the filling into one tortilla at a time, because a taco left standing softens through the base.