RECIPES AND NEW INGREDIENTS
Grimbrosia Source
No true gardening harvestable in this pack, though if you play the Reaper career you will gather Grimbrosia Source at some point during it. This grows from the ground and is used in a recipe, but doesn't exist outside of the career/debug.
Grimbrosia
Grimbrosia Source is used to cook Grimbrosia for Grim himself. It looks like Ambrosia, but can't be eaten by anyone but Grim and can't leave Headless Quarters due to being a propriety substance. Excess Grimbrosia you make can be sold (for §625, iirc) or converted into Ambrosia Pet Treats for Cats/Dogs or Horsebrosia, for Horses. So it seems like Grim is a softy for animals once again, but a bit tight when it comes to employees. Giving Grimbrosia to Grim improves your relationship with him, so you might want to keep any extra for that purpose too.
Death Frog
There is also one new collectible Frog that is used in a new recipe. The Death Frog. This frog has a fancy glass and brass terrarium and a skeleton design on it's skin. Due to being undead, it's not suitable to be bred. So far I've found them near Edith's Well and in the frog hunting fountain in the square during Ravenwood Family Day Festival.
Boiling Death Frog Hot Pot
This Frog can be used to make Boiling Death Frog Hot Pot. This dish, when eaten by living Sims, has the same effect as the Baleful Bog. You get turned into a temporary Ghost with a random Death Trait and a warning to not do it too often. Due to the warning being the same as the Bog, these are likely stackable, meaning the Boiling Death Frog Hot Pot could potentially kill you. Eating the hot pot as a Ghost is beneficial as it will refill your Stamina, allowing you to get your spook on.
Buffet Tables
This pack uses BG food Buffet Tables (like the ones from the Acting Career) for the most part, so there are no new Food Stands in the world. The festivals all seem to spawn basic food like Pizza, Burgers, Chips & Salsa and Mac & Cheese... The good food is found at Afterlife Anonymous. They have a table that spawns Gourmet Cooking dishes like Baked Alaska, and Lobster Thermidor.
If there are other recipes I haven't found them yet. I did check the Restaurant settings menu, but Boiling Death Frog Hot Pot wasn't on it, so they might have forgotten to add them to the UI again. I also haven't checked on a high-level chef yet.