Sift the flour, Splenda® Granulated, cocoa powder and salt into bowl and set aside.
Combine the hot water, instant coffee and vanilla and set aside.
In large mixing bowl, cream the butter until smooth. Stir in half of the dry mixture, then stir in the coffee mixture. Add the remaining dry mixture and combine.
Tip the dough onto a work surface and evenly divide into two pieces. Shape each piece into a log. Wrap each log separately and chill in the refrigerator for at least 20 minutes.
Preheat the oven to 160°C/Gas Mark 2½. Line a baking tray with parchment paper.
Unwrap the dough and slice into cookies about 1cm (½in) thick and place on the baking tray. Sprinkle each cookie in the centre with a pinch of Splenda® Granulated and bake for 18 minutes.