On the morning of the day prior to your khash feast, place the trotters in a large bowl and cover with water. Refrigerate at least 10 and up to 48 hours, changing water every two hours or so for the first 10 hours.
Place trotters in a heavy-bottomed pot and cover with 2 inches of water. Bring to boil over high heat. Regulate heat to maintain a simmer, and cook, uncovered, for 40 minutes.
Drain water, return trotters to the pot, and cover with 2 inches of fresh water. Bring to boil over high heat, reduce to simmer, and cook, uncovered, for 6 to 8 hours, topping up water every hour or two, until trotters are soft and tender.
Pour 2 cups of hot broth into the mortar or small bowl with the garlic and stir to combine.
Serve the remaining broth and meat immediately, passing salt, garlic mixture and optional garnishes. (Armenians recommend 4-6 cloves’ worth per person)
Khash can be made ahead through step three and refrigerated for up to four days. To reheat, simmer for 20 minutes.