Do you add the alcohol at the end or the beginning of the cooking? If it’s at the beginning, at least most of the alcohol will cook out. If you add it at the end, it’ll have a nice alcoholic zing! Haha. Even if you add it at the beginning, it might be good to add a touch at the end. I can’t say I’ve tried pure marsala or brandy, so I’m not really sure if the flavors would go well together. I would suggest trying it out in a sample of your custard to make sure the flavors go well before throwing them both in.
I haven’t made it, but I have made other custards – my advice is to make sure you cook it until it’s the right texture. I always tend to get impatient and pull it off before it’s thickened (but you might not have this problem!). I looked up a recipe and it looks delicious! I think it would be a wonderful topping for a cake or fruit or any other dessert, really. (a friend of mine makes steel cut oatmeal, adds fruit, and pours an alcoholic custard over the top for brunch – this would be good with that too!)