The NPC called Hornsent Grandam (Hornsent’s Grandma) has a secret side questline in Elden Ring Shadow of the Erdtree DLC. This walkthrough shows the full solution.
Missable Warning: Steps 1-5 have to be completed before beating “Messmer the Impaler” main boss at Shadow Keep Storehouse. After this Hornsent Grandam will no longer talk to you and the questline can no longer be initiated. Steps 7-8 have to be completed after beating Messmer but before burning the Sealing Tree at Church of the Bud.
For the similarly named character “Hornsent” (the grandson of Hornsent Grandam) refer to Hornsent Questline.
Walkthrough
Step 1: First you must obtain the Storeroom Key. Go to “Belurat, Tower Settlement” > “Small Private Altar” (site of grace). From the site of grace, head up the stairs to go outside. Turn left and go up another 2 sets of stairs (past a samurai enemy). In front of you there will be a waterfall across a ledge. Circle around the right side to reach the waterfall. On the side of the waterfall is a room with a ladder, climb up the ladder to find the Storeroom Key on a corpse.
Step 2: Go back to “Small Private Altar” site of grace. After the site of grace take the path to the left across a bridge. At the end of the bridge turn left to find a locked door, use the Storeroom Key on it. Inside the Storeroom you find Hornsent Grandam (Hornsent’s Grandma), talk to her, exhaust all dialogue. This has to be done BEFORE beating the Messmer boss at Shadow Keep, after beating Messmer she won’t talk to you anymore.
Step 3: Defeat the boss “Divine Beast Dancing Lion” at the end of Belurat. It will drop “Divine Beast Head”, collect this (it’s not automatically given when defeating the boss, must pick it up from the defeated boss).
Step 4: Return to Hornsent Grandam in the storehouse. Equip the Divine Beast Head. Now she will talk to you again. Exhaust all dialogue. You will receive “Watchful Spirit”.
Step 5: Fast travel and come back to Hornsent Grandam. She will have new dialogue and gives you “Scorpion Stew”. Exhaust all dialogues.
Step 6: Defeat Messmer the Impaler main boss in Shadow Keep Storehouse (on top floor). If you need help getting to him, refer to Shadow of the Erdtree Walkthrough.
Step 7: Return to Hornsent Grandam. She will give Gourmet Scorpion Stew. Exhaust all dialogue.
Step 8: Fast travel and come back to Hornsent Grandam. She will now be sleeping and left behind another Gourmet Scorpion Stew.
This finishes the questline of Hornsent Grandam.
For all other quests check out Elden Ring Shadow of the Erdtree All Side Quests.
You can actually give the scorpion stew to the other Hornsent dude, the one who gave you the map of the crosses. You will receive 3 of these visage things.
I assume you can also give him the gourmet stew and that there is more to Hornsent Grandams quest than just obtaining a consumable.