Meanwhile, bring a large pot of water to a boil and salt it generously. Cut the leafy green tops of the bok choy off the white stems and drop into the boiling water. Cook until softened and bright green, about 1 minute. Transfer to a plate and blot dry with a kitchen towel. Put about ¾ of the greens into a food processor and add the cottage cheese, lemon zest and juice, and nutmeg; season with salt and pepper and puree until smooth. Chop the remaining blanched leaves and put in a mixing bowl.
Chop 4 of the white bok choy stems into bite-sized pieces and add to the bowl with the chopped leaves. Add the tomatoes, season well with salt and pepper, and drizzle a little olive oil over the vegetables. Toss well to combine.
Grill the pork medallions, turning once, until cooked through but still juicy, about 8 minutes total.
To serve, spoon some of the creamy sauce onto a plate and spread it into a thin layer down the center of the plate. Pile a little of the tomato salad on top. Arrange grilled slices over the top of the salad and drizzle the vinegar glaze over the meat.