Yep I have tried making them without suet using butter instead and they shrivelled up and went hard, not very nice. My recipe is to get a measuring cup of any type, but one that holds around 250ml of water is ideal. Fill it just over 1/2 full with suet and empty that into a bowl, then fill it to the top with flour and tip that in the same bowl. Add a pinch of salt and pepper. Mix well using a spoon with just enough water to make a soft, slightly wet dough then drop by spoonfuls into your stew or what have you. I used to make them quite firm and rollable but found this way makes even nicer, crispy on the outside but fluffy on the inside, dumplings. Sometimes I make them cheesy dumplings, make in the same way but before adding the water add a generous handful of grated mature cheddar and 1-2 tablespoons of freshly chopped parsley or frozen version is fine too, then mix as before. I use the atora vegetable suet and it turns out great xx