For the relish, halve and pit the avocado, scoop out the flesh and place in a small bowl. Cut tomatoes into small cubes. Clean the onion, peel the garlic and chop both into small cubes. Mash avocado with a fork and mix with remaining ingredients, season to taste.
Heat oil in a small saucepan to about 170 °C (cooking spoon test).
Meanwhile, press or finely grate the cooked, peeled potatoes, mix with the remaining ingredients and form into small dumplings with wet hands (similar to croquettes).
Carefully place them in the hot fat. Turn after about 1 minute and bake until done. Drain on a piece of kitchen paper. Do not bake more than 5 at a time!