I have been getting very frustrated with putting fondant over buttercream, and read someone had used apricot jam. Has anyone done this and had good success? What's the best process? Or any other things, simple syrup or something else?

What is your frustration with buttercream? I would think most people want to taste some sort of icing under the fondant.

If you're having issues with the fondant sagging, bulges or that sort of thing, maybe trying using ganache under fondant. It sets up much firmer than buttercream and allows you to get nice sharp edges and straight sides.

No matter how thin I spread it, it always oozes out the bottom and makes a horrible mess!

perhaps you need to make your BC a bit stiffer then? I usually use ganache under mine. tastes better, easier and quicker to make, and looks better under the fondant. Sometimes i use BC though, if someone Ive made a cake for specifically asks for no chocolate.. i do hate when they do that though lol

Do you use a whipped ganache or a poured?

You want to use a firm ganache recipe... ratio of 2:1 dark chocolate to cream or 3:1 milk or white chocolate to cream by weight.

A poured ganache wouldn't make the nice sharp corner and not set as firm.

I use BC. I'm not a fan of all of the chocolate. It is over powering and has a dry mouth feel because it is so thick and too rich (for me). Some love it... I am not a huge fan, and white chocolate makes me gag it's so sweet.

use the recipe above and spread it on. I dont spread mine on particularly thick, i know that most people do though, I put just enough on to cover any inconsistencies in the cake and give the fondant something to stick too.

I also prefer ganache under my fondant. I let it set up just enough to be spreadable, then apply as smoothly as I can. Then I chill for a little bit and go over it with a hot spatula, chill again. Then I use a pastry brush with hot water. It takes a few extra steps, but the results are soooo worth it.

I have never heard of the use of apricot jam. I do not use ganache as a coating just buttercream. However, my buttercream preference is Swiss which is smoother to use. I do find that American style or cream cheese is a little more challenging to get super flat since it does not chill as firm as Swiss or Italian.

I just got a request for an anniversary cake next weekend. They don't like buttercream and some of the family is allergic to chocolate. I read somewhere online about using apricot jam under the fondant but there isn't much on it. I've never tried marzipan but have been reading about that as well. I'd love any other suggestions on what I could use.

Swiss meringue works really well under fondant - if you crumb coat your cake and chill in the fridge, there won't be any "oozing" to worry about

Bakers from the UK usually use warmed apricot jam, then marzipan, then frosting or fondant. Seems like a lot of steps to me but they do make gorgeous cakes.

If your bc is oozing out from underneath your fondant, you might be using too much bc or too much pressure when you smooth your fondant.

are you letting your cake sit in a freezer for 10-15 minutes 1st?
that will buy you some time before BC becomes very soft again.

I use BC as I like the taster to have some frosting if they don't like fondant.

Planet Cake teaches to use thinned apricot jam to brush on the ganache to make it tacky so the fondant will stick.

I use swiss meringue BC too. It works wonderfully under fondant.