Method:

Preheat the oven to 180C and prepare a baking sheet.
Cream the butter and sugar until light and fluffy.
Add in the eggs and vanilla essence and whisk to combine.
Add the flour, salt and baking powder and stir until just combined.
Turn the dough out onto a lightly floured surface and roll to 1.5-2mm thickness.
Cut out 24 medium sized Christmas trees. Cut out circles in the centre of half the cookies. Transfer all the trees onto a plate or baking sheet and freeze the cookies for 30 minutes or until firm.
Bake all the cookies in the oven for 12-15 minutes
In the meantime, place one colour of sparkles in a blender or food processer and crush.
Remove the cookies from the oven and gently transfer the whole cookies onto a cooling rack, leaving the cookies with holes on the baking sheet. Spoon the crushed Sparkles into the holes until ¾ full. Return to the oven and melt for about 3 minutes.
Allow all the cookies to cool completely.
Decorate the candy Christmas trees with the royal icing and top with the Jelly Tots as ornaments. Place in the freezer until the candy is hard.
Take one of the decorated cookies, flip it over and spoon over 1 tsp of sprinkles on the candy hole.
Pipe royal icing along the edge of the cookie and take one of the whole Christmas tree cookies and attach it onto the decorated cookie to seal.
Allow to dry and repeat the process until all cookies are complete.