13 oz brussels sprouts, outer leaves removed, trimmed and finely chopped
2 tsp sea salt, divided
1/2 tsp cumin seeds
1/4 tsp each yellow mustard seeds and coriander seeds
1/3 cup fresh orange juice
1 tsp mild curry powder
1/2 tsp ground turmeric
1 small green or purple cabbage leaf
1 1-qt wide-mouth glass jar with lid, sterilized
To a large bowl, add brussels sprouts and 1 1/2 tsp salt. Using your hands, vigorously massage until softened and about 1/4 cup of liquid is released (10 to 15 minutes). Taste and add remaining 1/2 tsp salt, if desired. Cover and set aside.
Heat a dry skillet on medium-high. Add cumin, mustard and coriander seeds; toast, stirring, until they begin to pop, about 3 to 5 minutes. Transfer spice mixture to a spice grinder; grind to a fine powder.
Add ground spice mixture, orange juice, curry and turmeric to Brussels sprouts, massaging to combine. (TIP: Wearing gloves will prevent turmeric from staining skin.)
Transfer Brussels sprouts mixture and juices to a 1-qt wide-mouth glass jar. Using a spoon or your hand, press mixture down firmly to release liquid and remove any air pockets, pressing until mixture is completely submerged.
Arrange cabbage leaf in jar directly over top of mixture to keep them submerged in liquid; seal loosely with lid. Let ferment in a cool place away from direct sunlight, opening jar every 24 hours to release pressure, pressing down on cabbage as needed to keep mixture submerged in liquid, and tasting occasionally until desired tanginess is reached, 7 to 21 days.
Discard cabbage leaf, seal tightly and refrigerate for up to 12 months.