Some culinary and farming stuff that has probably been mentioned a bajillion times before by other people:
On what I imagine would be the quicker and easier end, recipes like making red sauce from tomatoes and mushroom soup from mushrooms. More sealed-jar-of-food recipes, like jams, soups, sauces, broths, pastas, and the like. Maybe new seeds/crops, like oats, rice, and possibly soy. Maybe milk substitute recipes from things like rice and soy.
On culinary stuff that might require new systems as opposed to just new recipes/crops, maybe keeping a cow or goat for milk (I imagine a goat would be easier to keep and support, should you be able to find one), or cattle mutants being able to produce milk for a hunger cost. Maybe crafting cheese from milk, if you can get the supplies and recipes for it. Cheeses that age better or keep longer (which would probably require more to make than shorter-lived cheeses). Maybe even diving for clams, though this might be limited to freshwater mussels, which apparently are less tasty than marine clams and dangerous to eat raw, until/unless ocean tiles make it in.