Interesting thing about comfort foods is that they usually tend to be quite bland. I guess when it's cold outside or you're feeling a bit down you don't fancy stimulating your senses too much. To the contrary - you want to dull them, warm them, lull them and put them to sleep.
Soups work well, never too spicy. Stews and casseroles, sauces you can mop up with soft bread and of course anything smothered in cheese and cream.
One of the best comfort foods I can think of is tartiflette: potato, onions and bacon dish baked with a whole (yes, whole, but it's the size of Camembert) Reblochon cheese. All the comfort factors there: cheese, sauce, potatoes, bland. And a bit of bacon which never ever resonates badly.
Cauliflower cheese must be second best. Do it heavy or light as you like and have either as a side for a meat dish or a full-on cheesy creamy feast.
This recipe is a halfway house. Spicing it aspires to some level of sophistication, the cream is diluted with milk and I'm not doing béchamel seeing as cream will thicken up by itself with no addition of flour necessary. But then of course a great big whack of grated cheese is added and baked to a satisfying, bubbly goldenness. So there - a dish ready to drown sorrow or a chill in.