MartavTaurus
It's pretty easy to make, I've done it. It's in her book, Simply Nigella. You have to blitz one of our posters to smithereens. Guess who!?
I think the photo shown by the OP is Nigella's original one in the book, or else OP has the same plates and worktop?
I haven't seen that Nigella recipe, but Delia Smith has a similar one in her book "How to Cheat at Cooking" That has a jar of Fairtrade chocolate truffle sauce, mixed with unsalted butter, creme fraiche and a tablespoon of cognac or dark rum.
M & S used to have the jars of Fairtrade chocolate truffle sauce, but have stopped keeping it, although they have (in the same short wide size and shape of jar - maybe from the same source? ) a Salted Caramel Sauce. I have made it with this and some broken walnuts.
Everyone should own that book. Recipes for delicious things without a lot of work. Hardback with the cover laminated in plastic - as all cookbooks should be