Ok, don't know how "Christmas-y" this is, but when I was little I used to LOVE to make "chocolate crunchies"!
You need:

500g chocolate (I use half dark, half milk chocolate)
25g coconut fat (next to the butter in the supermarket, I think it's called Copha?)
1/2 tbs vanilla sugar
200g Cornflakes (plain ones, not the sugar coated ones)

That's it! Just melt the chocolate together with the coconut fat and vanilla sugar, let it cool a little (chocolate still has to be runny, but you don't want the little ones burning themselves!) and then add cornflakes. Stir, then put little "piles" on baking paper. Let cool. DONE! Soooo yummy!!! You can also add nuts or mini marshmallows or whatever (more rocky road like then ). Super easy. And quick! And when you put them in a cello bag and add a nice ribbon, they make a great present, too!

Other than that I loved decorating Christmas cookies (and mixing the ingredients, and rolling the dough lol)
It's actually really easy to make the dough.
You need
60g Butter (normal salted one)
125g sugar
2 eggs
1 tsp grated lemon peel (or just use lemon essence like I do )
250g plain flour + 1tsp baking powder (or just use self-raining flour)

Beat butter, eggs, sugar until fluffy, then add the rest. Done! (Told you it was easy!) Then roll out on a floured surface and use some Christmas cookie cutters to cut out the desired shapes. Put them on baking paper and bake at 180C until golden (maybe 10min? can't remember!) . Let them cool before decorating. THE BEST PART!! use coloured icing to coat the cookies and/or use writing icing (or whatever it is called) for details. Anything goes. Mini M&M's, cashous, sprinkles, grated coconut (makes a great Santa Clause beard or great angel wings!) etc etc

Little tip: If the dough is too soft and and the shapes fall apart, this is because the butter is too warm (Christmas is TOTALLY in the wrong season in Australia - it's too bloody hot for baking), you could put the dough in the fridge for a while (as if, who's got the patience?) or just add more flour to make the dough firmer That's what I do.

Have fun!!!