The recipe is calling for heavy cream. Whipping cream will do fine, as well.

Now that we've thought about your question for a few years, it occurs to us - and we don't like to admit it* - that the recipe may actually be calling for evaporated milk. Many macaroni and cheese recipes specify evaporated milk, and your recipe may have been put together by a somewhat careless communicator who said "thick cream" when she meant "thick milk." We are not familiar with macaroni and cheese recipes that require the use of heavy cream.

The final option - and then we promise to shut up - is that she meant a cream or béchamel sauce. We've seen quite a number of macaroni and cheese recipes that mix the cheese into a white sauce. Sadly, without seeing your recipe, we don't know exactly what you need to use, but undoubtedly, given all these options, you'll find the right one yourself!

*We have no problem with evaporated milk in general, but don't think it makes a very special macaroni and cheese....