1.Preheat oven to 180°C (350°F). Grease deep 22cm (9-inch) round cake pan; line base and side with baking paper.
2.Stir bourbon and sugar in a small saucepan over medium heat, without boiling, until sugar dissolves. Blend or process chocolate and bourbon mixture until smooth. With motor operating, add butter, piece by piece, processing until combined. Add eggs, one at a time, processing until combined between additions. Pour mixture into pan.
3.Place pan in a large baking dish. Pour enough boiling water into baking dish to come halfway up side of pan. Bake about 30 minutes or until edge is set (centre will still be a little soft). Remove pan from dish; cool 10 minutes. Cover; refrigerate 4 hours or overnight until set.
4.Carefully turn cake out of pan onto serving plate; dust lightly with cocoa. Serve with double cream.
Boca negra, Spanish for `black mouth’, is a silky, fudgy, moist chocolate cake, and is so named as it will turn your mouth black with chocolate after just one bite.Note