what is mascarpone and where may it be found?
It is a soft, mild cheese (originally from Italy) and can be found in most large grocery stores these days (and definitely at Whole Foods if you have one near you). If you can't find it, you can substitute with a tablespoon of cream cheese or creme fraiche for this recipe. Cream cheese is a little saltier, and creme fraiche is tangier, but with such a small quantity it shouldn't matter -- you're just looking for something that will add a little creaminess.
soft Italian cheese; look in dairy/cream cheese department
You can find it in the fancy cheese aisle of your supermarket. If you don't see it ask for it, sometimes it's hard to spot if you have a large cheese selection there.
It typically comes in a lidded container - like what you'd find whipped cream cheese or sour cream in. mrslarkin has also provided a recipe for it, but you'd have to make it the day before you need it. http://www.food52.com/recipes...
I think if you're going to sub cream cheese for mascarpone you would need to add a little milk or cream to loosen the cream cheese up. It is much stiffer than mascarpone -- possibly because of the gums that have been added.