Let's be real: most of us aren't great at fractions when the oven is preheating. The simplest way to make 3/4 of a cup is to grab a 1/4 cup measure and use it three times. That's it. One, two, three pours, and you're done.
Pro tip: if your 1/4 cup is somewhere in the dishwasher of doom, don't panic. You can also use a 1/2 cup measure plus one 1/4 cup. That's two scoops total, which feels a bit more efficient, doesn't it? Efficiency is sexy. I don't make the rules.
If you're metric-brained and live in a world of grams, 3/4 of a cup is about 177 milliliters. But honestly, who wants to do math when there's chocolate involved? Stick with the scoop method, and you'll be fine.
