Position a rack in the center of the oven, and heat the oven to 400°F.
Toss the bok choy and squash with 2 Tbs. of the oil on a large rimmed baking sheet. Season with salt and pepper, and spread in a single layer. Roast, flipping once, until golden in spots, about 25 minutes.
In a small bowl, whisk 3 Tbs. of the oil, the teriyaki sauce, vinegar, ginger, and the chopped garlic.
Heat the remaining 2 Tbs. of oil in a large skillet, preferably cast iron, over medium-high heat. Press the pork medallions lightly to flatten a bit, then season with salt and pepper. Add the medallions and whole garlic cloves, and cook, flipping once, until browned on both sides, about 8 minutes total. Turn the heat off, but leave the medallions in the pan for a couple of minutes.
Divide the boy choy and squash among 4 plates. Top with the pork, drizzle with some of the sauce, sprinkle with the chopped cilantro, and garnish with the extra leaves. Serve any remaining sauce at the table.
