How to make butter and sugar mixture into a breadcrumb consistency?
Use chilled butter and don't touch it with your fingers unless you can be really fast about it, you don't want the butter to start to melt. Use a fork, a couple of knives or ideally a pastry cutter to cut up the butter and coat the cold little pieces of butter with the sugar.

 

You can even use a cheese grater to grate the frozen butter and toss the grated butter with the sugar.