In a small saucepan combine cream, 1/4 cup sugar, 1 tablespoon butter, golden syrup and chocolate chips. Cook over medium heat, stirring constantly, until mixture boils. Continue to cook while stirring for 5 minutes. Remove from heat and cool 10 minutes. Stir in nuts and vanilla.
Place cake on serving plate. Pour frosting evenly over cake, allowing some to run down sides. Arrange pecan halves on top. Refrigerate until frosting is firm, about 1 hour.