Preheat the oven to 170°C and line a 8x4 inch loaf tin with oil and baking paper.
In a medium saucepot heat the butter and oil on a low flame. Add the sugars, coffee, cocoa powder and whisk until combined. It wont be smooth but ensure there are no lumps.
Remove from the heat and let it cool for a couple of mins add the eggs one at a time beating well between each addition.
Add the flour, salt vanilla, walnuts and fold together mixing until smooth and combined. Do not over work the batter once the flour is incorporated and everything looks uniform stop mixing.
Pour the batter into the prepare tin and smooth it out with a spoon or spatula. Bake for 23-25mins until the top has risen, it’s dry to touch and a toothpick inserted comes out with moist crumbs.
Leave to cool in the tin for 30 mins, remove and cut into squares.