Baking experts - come and help me please!

[MacduffsMuff]

I want to make vanilla cupcakes and chocolate cupcakes today. I really want to just make one batch of vanilla and chuck a load of cocoa powder in half of it for the chocolate ones but some recipes say this is fine while others say you should substitute some flour for cocoa powder, so that would mean two batches. I've also heard of making a chocolate 'paste' with water and cocoa and adding it to vanilla mixture - is this a good/bad idea? Would really appreciate some pointers, thanks!

I would just add the cocoa powder to half the mix and if it seems a bit dry, add a splash of milk.

I've made chocolate cakes using your first method; cocoa powder in half the vanilla mixture. It worked, and nobody complained.

Normally I would substitute some of the flour for the cocoa powder but if you are using half of the plain cake mix then adding a splash of milk should do the trick.

Thank you!