Hi everyone.

So I have found an amazing Vanilla cupcake recipie that I have tweaked until perfect. But now I want to turn it into chocolate. It makes a perfect dozen cupcakes, so I don't want to mess with volume. So how do I go about changing it to Chocolate? Can I just remove some flour and replace with cocoa? Or maybe add some melted chocolate?

Any advice is appriciated!

thats what i would do, get a really good cocoa and then just subsititute that for a percentage of the flour x

yes you can substitute 25% of the flour with cocoa by weight (not volume) but keep in mind cocoa has diferent properties than flour so will change the texture and sometimes the levening.
try adding equal parts cocoa and water together to make a thin paste and add it to the batter.
or a little oil
sorry to be vague but experienting is the best way, since you know what results you are looking for.

example: i make a vanilla batter, pour 1/2 in pans then add cocoa-water paste to remaining batter, mix, and marble into the pans...