Start by removing the stem from the leaves, cutting them from inside the leaves. Cut the leaves in squares, about 7-8cm each and keep aside.
Going back to the stems, finely chop them to almost the same size of the chopped onion.
Get a very large pot or casserole or sauteing pan and place on medium heat. When it heats up pour the oil and allow to heat for about 1’. Add the onions along with the chopped chard stems and sauté for 4’. Then add the garlic along with the thyme, coriander, nutmeg and season with the salt and pepper. Keep sauteing for 2’ more.
Then drop in the cut leaves, toss well, cover with a lid and allow to soften and wilt for 3’. Uncover, pour the balsamic vinegar and toss for a minute more.
Remove from the heat and place in a bowl to serve.