Process the walnuts in a food processor until coarse and sticky. Add cocoa powder and salt to this mixture. Next, add the dates, a little at a time, and keep blending until it becomes like cake crumbs. Keep adding dates until the mixture sticks together. Transfer to a dish/mould and set to desired shape. You may chill this for about 1 hour or serve immediately. Cut into squares or wedges before serving. Keep refrigerated to store.