Trim the cauliflower or romesco, discarding any very thick stalks or tatty leaves. Cut into small florets. Put a large, deep pan of water on to boil.
Top and tail the green beans and cut into short, 3cm lengths. Peel the shallots then halve each one.
Put the cauliflower florets into the boiling water for 3 minutes, then lift out with a draining spoon and plunge them into iced water. Do the same with the beans.
When the water returns to the boil, add the shallots and cook for 8-10 minutes until almost tender, but still with a crunchy texture. Lift out and set aside.
Roughly chop the tomatoes and put them in a saucepan with the gochujang and the vinegars and let them simmer for 10 minutes until the tomatoes are soft, crushing them with a spoon as you go.
Using a stick blender, purée the tomatoes and spice paste until smooth.
Mix the cornflour to a thin paste with a little water then stir into the tomato mixture and bring back to the boil. Immediately the tomato purée starts to thicken, remove from the heat.
Drain the cauliflower, beans and shallots, stir them into the tomato purée and spoon into a clean storage jar. Seal and refrigerate.