I need a good tasting, moist, firm cake recipe that I can use under my fondant.

any ideas? also a good vanilla and chocolate filling!!

I am making a birthday cake and want to be very impressive

Hi and Welcome to CC, Sahar78.

Everything you need to know to make, decorate and assemble tiered/stacked/layer cakes:

http://cakecentral.com/cake-decorating-ftopict-605188-.html

Above superthread has popular CC recipes for crusting American b/c's, several types of fondant and doctored cake mix (WASC and other flavor variations) - and so much more!

Vanilla custard filling:

http://cakecentral.com/recipes/7399/vanilla-custard

Costco mousse filling:

http://cakecentral.com/recipes/7308/costco-mousse-recipe

Chocolate mousse:

http://cakecentral.com/recipes/5443/chocolate-mousse

Whipped chocolate ganache:

http://cakecentral.com/recipes/2328/whipped-chocolate-ganache

Fudge filling:

http://cakecentral.com/recipes/4003/fudge-filling

Easy and Tasty cream cheese filling:

http://cakecentral.com/recipes/2743/easy-and-tasty-cream-cheese-filling

HTH