Missing butter in ingredients - It says "add the butter" but how much and should it be softened, cold, melted?

I am not the original recipe writer, so the best I can do is give you a guess. I make a similar type crumble to use for things like this, or pies. After I've mixed the sugar and flour, I grate in about 10-12 tablespoons of butter, and then cut/mix that in with a fork until it's crumbly. I've never gone as far as breadcrumbs, but I don't see why you couldn't. The finer the mixture is going on, the less "crumbly" it ends up, but it's still tasty. You can also vary the type of sugar you use, and use a combo of brown and white sugar if you like, or stick with all one or the other, and it still works fine. You can also add in spices to your liking, before you add in the butter. You also don't have to grate the butter, but I find it easier to do the mixing that way. You can simply cut it in with a dough cutter, or use a food processor. The butter does need to be cold though, melted butter will just get you a mess and not a crispy crumble.