Cream sugar and butter in a bowl with an electric mixer until creamy. Add eggs, 1 1/2 teaspoons vanilla extract and almond flavouring; mix well.
Stir flour, baking powder and salt together in a second bowl. Add flour mixture to the creamed butter mixture and mix to combine. Wrap in cling film and chill in the fridge for 3 to 4 hours or overnight.
Preheat oven to 180 C / Gas 4. Line 2 baking trays with baking parchment.
Dust a work surface with 2 tablespoons icing sugar and roll out dough into a 1/2cm thick circle. Cut out figure shapes with a gingerbread man cutter and arrange cut-out cookies on prepared baking trays.
Bake in the preheated oven for 8 to 10 minutes. Remove from baking trays carefully and transfer to cooling racks. Cool completely, about 20 minutes.
To make the icing: Stir icing sugar and milk together in a small bowl until smooth. Beat in golden syrup and vanilla extract until icing is smooth and glossy. Add more golden syrup if icing is too thick.
Spoon icing into a piping bag with a small plain tip. Draw a filled-out circle inside the head for the skull and a skeleton on the body, including 3 horizontal lines for the ribs. Let cookies stand until icing dries completely, about 2 hour, best overnight.
Use black decorating gel to draw eyes, a nose and a mouth on the skull and let cookies dry again, about 1 hour.