Trim pork tenderloin and slice into 1-inch thick medallions. Season with salt and pepper. Slice leeks (white and light green parts) and apple into thin half-moons. Dice potatoes into 0.5-inch cubes.

Heat half of the olive oil (10g) in a large skillet over medium-high heat. Add pork medallions and sear for 3-4 minutes per side, until golden brown and cooked through. Remove pork from the skillet and set aside.

Add the remaining olive oil (10g) to the same skillet. Add diced potatoes and cook for 5-7 minutes, stirring occasionally, until they start to soften and brown. Add sliced leeks and apples to the skillet. Sauté for another 3-4 minutes until leeks are tender and apples are slightly softened.

Stir in vegetable broth, Dijon mustard, and fresh thyme. Bring to a gentle simmer, scraping up any browned bits from the bottom of the pan. Return pork medallions to the skillet and coat with the sauce. Cook for 1-2 minutes to warm through. Serve immediately.