Preheat oven to 180C/160C fan-forced. Grease the base of a 22cm round springform cake pan and then line base and sides with baking paper.
Use an electric mixer to beat butter and sugars in a bowl until light and fluffy. Add egg and Baileys. Beat until combined. Sift flour and bicarbonate of soda over mixture and then beat until combined. Stir in chocolate.
Press mixture into prepared pan. Flatten the surface. Bake for 35 minutes or until golden. Cool and rest in pan for 10 minutes.
To make Baileys Chocolate Sauce, place cream in a small saucepan. Bring to a simmer over medium-high heat. Remove from heat and add chocolate. Stand for 5 minutes and then whisk until smooth. Add Baileys and whisk again. Cover to keep warm.
Serve warm biscuit drizzled with sauce and topped with vanilla ice-cream.
