Butters in the states have gradations marked on the wrapper, and then you just cut down with a knife at the proper marking. Don't know if that'll help in a non-cup-based system! alternately, find the density of butter, convert the 3/4 cup measurement to a mass, and just weigh it out on a scale...

Looks like 3/4 cup is 177 mL, and the density of butter is .911 g/mL. Therefore 3/4 cup is ~162 grams. If this helps?