Woodcraft expansion!

new construction: improvised woodcraft shelter
new trees: pine trees - found in forests
new trees: dead pine trees - found in forests or caused by picking live pines
new food source: pinecones - found on the ground in forests or by picking pine trees
new flowers/food source: dandelions - found in meadows
new food source: morel mushrooms - found with other mushrooms when foraging
new food source: buckwheat - found by foraging
new food source: dahlia root - found by picking dahlias with a digging tool in your inventory
new food source: acorns - found by foraging and on the ground in forests

many new recipes, items, foods, and drinks
many modified recipes that use new ingredients
There's nothing wrong with the plurality (making mushroom plural would be wrong, I think, e.g. "A tasty serving of cooked carrot" - it doesn't matter how many carrots were used), but I agree that if a serving always consists of a single mushroom, then you might as well remove "serving of".  You'd only need "serving of" if a serving consisted of more or less than exactly one mushroom.  Like if you cooked multiple mushrooms in a pot, mashed it up, then started serving that.