Make the meatballs. Mix together all the ingredients in a bowl and season. Knead the mixture well, then roll cherry-sized pieces into firm balls.
Pour the measurement water into the base of a tagine or a large, heavy-based saucepan and bring to the boil. Add the meatballs, a few at a time, reducing the heat to a gentle boil, and poach the meatballs for 10 minutes, turning occasionally, until cooked through. Remove with a slotted spoon and drain on kitchen paper.
Pour about 125 ml (4 fl oz) of the cooking liquid into the base of a tagine or a large, heavy-based saucepan and bring to the boil. Stir in the butter, salt and cayenne, then add the poached meatballs. Make 4 wells, then break the eggs into the wells, cover and cook for 5–6 minutes, reducing the heat slightly, until the whites are just set but the yolks are still runny.
Meanwhile, dry-fry the cumin seeds in a small, heavy-based frying pan over a medium heat for 1–2 minutes until they emit a nutty aroma. Tip into a spice grinder and grind over the eggs. Garnish with the parsley and serve immediately, with buttered toasted flatbreads, if liked.