2 medium Asian eggplant – cut into 1 inch thick pieces on the bias
8 ounces yardlong beans (sitaw) – cut into 2 inch lengths
1 bunch bok choy (pechay) – halved lengthwise
bagoong alamang (fermented shrimp paste) – for serving
Instructions
Combine the oxtail and water in a large pot, bring to a boil over high heat, skim foam, then reduce to a gentle simmer, partially cover, and cook until the meat is very tender and nearly falling off the bone, 2–2.5 hours; measure out 6 cups of the cooking broth and keep hot.
Make the color base: In a large Dutch oven, warm the neutral oil and annatto seeds over low heat until the oil turns deep red-orange, 3–5 minutes; strain and discard the seeds, leaving the annatto oil in the pot.
Add the onion and garlic to the annatto oil and cook over medium heat until soft and sweet without browning, 4–6 minutes.
Build and thicken the sauce: In a dry skillet, toast the white rice over medium heat, stirring constantly, until deep golden and nutty, 5–7 minutes; cool briefly and grind to a fine powder. In a food processor, grind the roasted unsalted peanuts to a fine meal. Whisk the ground peanuts and natural peanut butter into the pot with the aromatics, then slowly pour in 4 cups hot reserved cooking broth, whisking until smooth. Sprinkle in the toasted rice powder while whisking and simmer until glossy and thick enough to coat a spoon, 6–8 minutes.
Add the cooked meat and, if needed, 1 more cup hot reserved broth to loosen; simmer, stirring occasionally, until the sauce clings nicely, 10–15 minutes.
Blanch the vegetables: In a saucepan, bring 1 cup hot reserved broth to a bare simmer. Add the yardlong beans and cook until crisp-tender, 2–3 minutes; lift out. Add the Asian eggplant and cook until just tender, 3–4 minutes; lift out. Add the bok choy and cook until bright and tender, 1–2 minutes; drain well. Fold the vegetables into the stew just before serving and season the sauce with the fish sauce and the kosher salt (start with 1.5 tsp), adjusting to a savory but mellow finish.
Ladle into a serving dish and present with the bagoong alamang on the side.