You can change the method and get a finer result by beating the softened butter with the oil and sugar, then the eggs, then the chocolate, coffee, flour and nuts. But that means more work, and more bowls to wash, when, surely, the only essentials are a magnificent flavour and a sticky, moist texture. Rye flour gives the brownie a lovely taste, but use plain if that's all you have.
125g unsalted butter
75g hazelnut oil
300g dark chocolate, chopped
275g light soft brown sugar
3 large eggs
75ml strong black coffee
250g rye flour
¾ tsp baking powder
150g toasted hazelnuts, skinned
Melt the butter in a large saucepan, then add the oil and chocolate, and stir over a low heat until melted. Beat in the sugar and eggs, then the coffee. Beat in the rye flour and baking powder until smooth, then stir in the hazelnuts. Spoon into a deep, 20cm-25cm square cake tin lined with foil and bake at 180C (160C fan-assisted)/350F/gas mark 4 for 30 minutes; check it five minutes before the end, just in case the oven cooks it too quickly - it's always better slightly to underbake a brownie. Just stick a toothpick in the centre - if it comes out with barely cooked and sticky crumb on it, it's done. Remove from the oven and leave until the brownie is completely cold before cutting.