What sides should I make with beef Wellington for Christmas dinner?

Will definitely be dauphinois and crunchy greens on my plate!

I agree that a decadent dish like this could still use even more decadence...for those that choose this route anyways. I would Hasselbeck the hell out of something...and maybe a brussel caesar with Bloomfields dressing recipe [which i have adapted to my own]

I think decadent potatoes - your aligot, or mashed or dauphinois or "melting" - and a crisp simple green vegetable. I like to steam string beans, broccoli or brussels sprouts until al dente, then finish in a saute pan with butter and lemon for acidity, a handful of toasted almonds shaken over.

I think if you’re going to go big, go all the way....I think aligot sounds delicious! However, with a rich dinner I generally serve a condiment that’s sharp and acidic to help cut the fat. I love a good giardiniera, bright chutney or quick pickle. You could throw one together (I love a good roasted onion-grape chutney) or a specialty market might have a good prepared variety. I just look for something that’s bright and zingy to contrast all of the fatty, rich flavors. That and of course a green veggie.

Whenever I've ordered this at s restaurant they served it with mashed potatoes and a green vegetable. The Beef Wellington is the star so sides IMO should be simple.

Who's at your table that day, and what would please them most?
Do THEY go for utter decadence on Christmas!
If yes, full steam ahead.
If not sure, go simple but good.
Or have a choice of rich and simple side dishes.
Think of simpler but good potato dishes and and a dark green salad or roasted green vegetable.