Peel, trim, and cut carrot into 1/4" slices on an angle. Stem cilantro, mince stems, and coarsely chop leaves. Remove any discolored outer leaves from bok choy and trim ends. Cut stems into 1/4" slices and coarsely chop leaves. Pat pork tenderloin dry. On a separate cutting board, slice tenderloin into eight medallions 1/2-3/4" thick. Season both sides of medallions with 1/2 tsp. salt and 1/4 tsp. pepper.

Heat 1 tsp. olive oil in a medium non-stick pan over medium-high heat. Add medallions to hot pan and cook until well-browned on both sides, 3-4 minutes per side. Transfer medallions to a plate. Pork will finish cooking in a later step. Reserve pan; no need to wipe clean.

Heat 1 tsp. olive oil in a large non-stick pan over medium-high heat. Add carrot to hot pan and cook undisturbed until lightly charred, 2-3 minutes. Reduce heat to medium and add 1/2 cup coconut milk, 2 Tbsp. water, ginger, and cilantro stems. Bring to a simmer, add bok choy stems, and cover. Cook until carrots are tender and coconut milk is slightly thickened, 4-6 minutes. While vegetables cook, glaze pork.

Return pan used to sear pork to medium-high heat. Add tamarind, sweet chili sauce, and 1 Tbsp. water to hot pan and stir. Bring to a simmer and return pork medallions and any accumulated juices to pan. Cook, flipping medallions occasionally, until pork is glazed and reaches a minimum internal temperature of 145 degrees, 1-2 minutes. Remove from burner.

When carrots are tender, add bok choy leaves to pan with other vegetables. Stir and cook until leaves are just wilted, 1-2 minutes. Season with 1/4 tsp. salt and a pinch of pepper.

Place vegetables on a plate and place pork medallions next to them. Drizzle pork with any remaining glaze from pan and garnish vegetables with hazelnuts and cilantro leaves.