Help! Looking for Christmas desserts that can be baked in advance!

Consider a steamed pudding, which will hold beautifully for several months, and indeed, will improve with time if tightly wrapped. Here is my recipe, which can be made in a full pudding mold instead of smaller portions steamed in Mason jars or ramekins. https://food52.com/recipes/31848-steamed-holiday-pudding-the-mason-jar-edition

If you don't have a pudding mold, see this marvelous video from the BBC, on how to make do with a bowl, foil, parchment and string: http://www.bbcgoodfood.com/technique/how-steam-pudding

To serve on a festive occasion, don't forget a good brandy or sherry sauce! Here is my recipe for the latter. If you don't have sherry, or are not terribly fond of it, substitute brandy, of course. https://food52.com/recipes/32024-amontillado-dessert-sauce

I'll be posting several other recipes for holiday dessert sauces in the next few weeks, too.

Keep in mind that any of the sauces can be used over a simple pound cake, which most people love, and which freezes beautifully. Cheers! ;o)

Just saw this article on freezing pies and noticed two things: fruit pies OK to freeze but it doesn't recommend freezing custard or pumpkin pies. And Pyrex or glass pie dishes are not recommended (use tin or ceramic like Emile Henry) because of the sudden temperature shift from frozen to hot - the Pyrex or glass can crack.
http://www.thekitchn.com/freeze-your-unbaked-pies-to-save-time-on-thanksgiving-thanksgiving-tips-from-the-kitchn-212636

Fudge!!

I always have chocolate mousse and lemon curd in my freezer. Get a variety of berries, whipped cream, chocolate syrup and people can made their own!

Most of the do-ahead desserts have been covered here, but I have to add a couple. Frozen mousses are very festive, easy and you MUST do them ahead and freeze them. Also chocolate truffles can be frozen successfully. Just make sure you thaw them completely before boxing them with candy papers, as the moisture would make the little cups soggy.

I love fruit cake too (but without the green cherries). Nannydeb's "Holiday Fruit & Nut Cake" is very good: https://food52.com/recipes/8220-holiday-fruit-nut-cake

This Date, Apricot and Walnut Loaf Cake that was recently featured on the site is SO good. It's a sophisticated version of fruit cake, and it gets better with age so you could bake it three or four days in advance with no need to freeze it. https://food52.com/blog/11454-diana-henry-s-date-apricot-and-walnut-loaf-cake

Fruit cake (I know, I know) should be made at least a month in advance. If you think you hate fruit cake, you could try this recipe - http://chowhound.chow.com/topics/269321. It is really not what you would expect fruit cake to be and it is very, very good.

Cake! Cake! Any (unfrosted) cake!

Just saw this great recipe for rugelach (delicious - more of a pastry than cookie)
https://food52.com/blog/11669-mrs-wheelbarrow-s-rugelach#tmhmdj:SGy

You could also bake and fill little tartlets with lemon curd, jam or conserves, then freeze. Defrost and add a dollop of whipped cream before serving.

Many types of cookies, plus brownies, blondies, etc. freeze well. Cheesecakes generally freeze well too (though if you're topping it with fruit, do that after defrosting.) I've frozen flourless (or near flourless) chocolate cakes and they were fine - just serve 'as is' with whipped or vanilla ice cream.

Unbaked double-crust fruit pies freeze very well. You just need to add more baking time to defrost them when you finally put them in the oven. You can also freeze unfrosted layer cakes, defrost later, then frost, glaze or add toppings the day before or day of. Same with "loaf" dessert breads or bundt cake. Trifles are easy to assemble (fun for kids as they don't need much precision) and could be made quickly the day before or day of. Nigella Lawson has a very tasty chocolate cherry trifle - check her web site.