Hi!  I am making a Harvey Wallbanger cake that I want to cover with fondant but I am unsure what I should fill it with and crumb coat.  I found this recipe online.  Can it be used under fondant?  Any other filling/crumb coat suggestions? 

1/2 c (4 oz) mascarpone cheese
1/6 c (39 ml) well-chilled heavy cream
1/8 c (25 g) sugar
 

TIA!

I use Marscapone cheese all the time.....I love it..can eat it with a spoon...but it is still just Cream Cheese...just "Italian" cream cheese.   I, personally, would never use any type of cream cheese icing under fondant.    Especially the recipe you have posted.  It is going to be super soft...super yummy...but super soft.  You can use it as the filling, but I would not use it as an icing.   I am also not familiar with the Harvey Wallbanger cake...I only use butter cream or ganache under fondant.