Preheat oven to 175° C (350 F).

In a small saucepan over very low heat, melt the butter, but don’t let it become hot (you can also use a microwave for this).

Beat butter and sugars in the bowl of a stand mixer fitter with the flat beater until mixed and creamy.

Add eggs and vanilla and beat a few seconds to combine. In another bowl, mix together the flour, cocoa, baking soda and salt.

Add this mixture to the mixer bowl and beat to incorporate. Beat in briefly (or fold in with a spatula) the chocolate chunks and walnuts. You will have a rather wet dough.

Line baking sheets with greaseproof paper or silicon mats. Use a cookie scoop or a tablespoon and spoon golf-ball size balls on the baking sheet. Don’t put them close together as they will spread during baking (I put 8 balls on each cookie sheet).

Bake for 9-10 minutes. The cookies will be very soft when you take them out of the oven and will look as if they need more baking. They don’t. The cookies will harden as they cool and if you over-bake them they will be rock hard when cool. They should be soft in the centre and just cooked around the edges.

Leave cookies to cool in the baking pans for 20 minutes or so. Then remove them to plates. Eat them warm or cold with a jug of cold milk.

Note: If for a reason I fail to understand, you wish to half this recipe, use ¼ cup plus 2 Tbs cocoa.