Serve this delicious sauce over your favorite pasta for a quick, delectable meal. Do NOT substitute half-and-half for the heavy cream if you want a thick sauce. Heavy cream contains at least 36% milkfat. Half-and-half, just like the name says, is half milk and half cream and is no more than 18% milkfat. If half-and-half is used, the sauce will only be half as thick as it would if heavy cream were used. Also, if the amount of butter is reduced, that will also make the sauce thinner, as butter is 80% milkfat.