Are mascarpone and clotted cream the same thing?
They are completely different.

Clotted cream, also called Devonshire cream, is made by heating unpasteurized milk until a layer of cream forms on the surface. The mixture is then cooled, and the cream skimmed off. It has a butterfat content between 55 percent and 63 percent. Unlike creme fraiche it is not a cultured milk product, and is typically eaten as a tea-time accompaniment to scones or bread. Clotted cream is also naturally thickened by the heating process, whereas tartaric acid (a thickening agent) is added to mascarpone to create a firmer, smoother texture.

Mascarpone is classified as a curd cheese, unlike clotted cream and creme fraiche. The fat content in mascarpone is 25 percent. It is made by heating cream and adding tartaric acid to the mixture to further thicken it. The mixture is then cooled and strained, yielding the creamy-textured mascarpone. Mascarpone may be used as a dessert filling or as a thickener in savory sauces. Some methods of mascarpone production call for initially culturing the cream prior to heating and mixing it with tartaric acid.