Wash the vegetables, peel and finely chop the carrots and onions. Dice the zucchini finely, as well as the celery and parsley. Cut the peeled potato into small cubes.
Pour the chopped vegetables in a pan with heated oil. Total mass needs to be about 17.5 oz (500 g).
Cook 10 min. until softened, then sprinkle salt, black pepper and the spices. Stir well, add the butter and cook another 5-10 min. Remove from stove, leave to cool a bit, pour into a chopper and chop to a paste.
Distribute the paste onto baking paper into small rectangles and put in the freezer for 10-12 hours to harden. Take out and cut into cubes (size of your choice) with a sharp knife to end up with broth cubes.
Place each onto a cut square piece of baking paper and arrange in a container, store in the freezer because these have no preservatives aside from salt, unlike store-bought ones.