
Mascarpone is a soft, fresh Italian cream cheese, thick and only faintly tangy.
A spoonful gives a dessert drink body and a creamy richness. It suits coffee and chocolate drinks in the tiramisu style. If the drink is shaken, loosen it with a little cream first; a cold lump will not disperse and leaves flecks.
Full-fat cream cheese
The closest swap, in the same amount. Mash it smooth with a spoon first. Expect a tangier, cheesecake-like result.
Clotted cream
Use the same amount for a richer, heavier result with a faintly cooked taste.
In the same amount gives most of the richness without the cheese, and a thinner drink.
The cream is set with acid rather than rennet and never aged, so it tastes more of cream than of cheese.
Keep it refrigerated and tightly closed, and use it by the date on the tub. It is a fresh cheese with nothing to preserve it, and an open tub picks up fridge smells.