AI have only 200 grams of baking chocolate. I wanna make chocolate ganache. how much cream do I use? and also do I use butter in ganache? cuz I saw sometimes recipe has butter but most don't... so no butter right?

do you have whte or milk/dark chocolate? if white use 65ml of cream, if dark/milk use 100ml of cream

i have semi sweet chocolate.. is it the same as dark? 

What are you using it for?

i using it for a cake... i need more chocolate right? 

ATo cover a cake you will most likely need more chocolate, but I wouldn't use baking chocolate. I always use eating chocolate or couverture chocolate.

oh okay 

Are you covering the cake with it? Filling the cake with it? drizzling it over a cake already coveed with buttercream?

To cover and fill and 8 inch cake for under fondant, I typically use about 1kg of chocolate (Nestle melts usually) and 500mL of cream for dark choc, and 300mL for milk/white choc.