I want to replace a white (granulated) sugar in a recipe with brown sugar. Is this a one to one substitution?
The original recipe calls for 2 cups white sugar. Can I replace with 2 cups brown sugar? Packed or unpacked?
Yes you can...by volume. You'll definitely need to pack the brown sugar. The taste will be different (obviously) and the weight will be slightly different as well, but it'll work. Mind you, brown sugar does not dissolve the way white sugar does, so you may get some crunching if you don't combine it with your wet ingredients first.
Don't substitute by weight. Brown sugar weighs more.
Its also worth noting that brown sugar is actually molasses and regular suger. Molasses has some diffrent properties like beeing higher in simple sugers meaning that it'll taste sweeter than regular sugar.
if you do substitute them one-to-one expect the cake to taste sweeter than it normaly would have.