Why do some people use a ratio of 2:1 (chocolate and cream) when making ganache for covering cake before covering in fondant and others use a ratio of 3:1 of chocolate and cream? I don't want to make it really hard, I want it to be truffle like.

It depends on your personal preference and the type of chocolate you use. A milk chocolate will require more chocolate than a bittersweet chocolate will and white chocolate will require even more than a milk chocolate since there are no cocoa solids in it.

I like a 2:1 ratio for darker chocolates to cover a cake before fondant... for a filling (or truffles) I'll do 1.5:1 chocolate to cream ratio and for whipped ganache a 1:1 ratio (all these ratios assumes the use of a semi-sweet or bittersweet chocolate). White chocolate requires at least a 3:1 ratio to coat a cake before fondant and I have never used it as a filling... it also takes longer to set up so you can use it. I don't much care for white chocolate ganache really, but I am not a sweet-lovin' person and prefer my chocolate to be at the most semi-sweet. If you are looking to just cover the cake in ganache and not apply fondant you could use the 1.5:1 ratio and it's quite nice. Goes on like buttercream when slightly warmed and will firm up to truffle consistency when cool.

(These are just my opinions and what works for me)

For a filling, you might use more cream to get a softer, truffle-like texture. But for the outside of the cake as a base for fondant, the lower ratio makes things easier. The 2/1 ratio gives a sturdier texture so that you can obtain a perfectly smooth, but firm, base to support the fondant. By using the firmer texture, you avoid problems like sagging and bubbling, which can happen to fondant applied over buttercream, for example.

Hi, 1:2 ratio of cream to choc is for dark chocolate. And 1:3 ratio is for white chocolate.

BOth gets hard but its not difficult to cut into the cake. It gives a nice smooth finish to the cake and when you put fondant, its flawless. But if you want to make an all chocolate cake, then 1:1 ratio of cream and chocolate is great. YOu can just pour over the cake and it gives you a nice finish. And if you want to have a shine to the end product, add some butter to the poured ganache.

thanks