I’m probably not the only one that ends up with ridiculously huge amounts of berries in my inventory. I would suggest letting the cook make pies, pastries and maybe things like jams or jellies. These items could be higher level and add happiness and maybe a production buff to the hearthlings that eat them. Otherwise, it seems that no one eats the berries anymore once better food is being produced.
Don’t forget the pricklypear pies ! XD I usually sell them off ad that point, just some easy cash.
If you have the storage space, berries can be a small additional export to sell to traders.
But if you want pies right now, check out the Cafe Mod: [MOD] Stonehearth Cafe (Cooking And Farming Expansion) 1.92.
I do sell the berries all the time. I just thought it would be cool if there were more uses for them.
It would be interesting if things like berries or carrots or turnips (low level not super nutritious foods) could be used at later levels to increase the capabilities of higher level foods - Pies or pastiers as you suggest, but also side dishes or healthy snacks or fine restaurant dining, etc. In a gameplay sense, they could be eaten with any other meal and provide some sort of benefit - or could make a new 5 course meal for the little hearthlings.
This because PIES!!!
Even adding a simple thing like Berry punch to drink with the hearthlings meals could be super beneficial.