Season both sides of the pork medallions with salt and pepper. Heat 1 tablespoon of olive oil in a large skillet or sauté pan over medium-high heat. Once hot, sear the pork for 3 minutes on each side, until nicely browned. Remove from the pan and set aside.

Reduce heat to low-medium and add the remaining olive oil. Stir in the minced garlic and sliced leek, sauté for 1-2 minutes until fragrant and softened.

Add butter and sliced mushrooms to the pan. Saute for about 2 minutes, until the mushrooms start to soften. Pour in the white wine to deglaze the pan.

Stir in Dijon mustard, Worcestershire sauce, soy sauce, mushroom seasoning, a pinch of salt, and red pepper flakes (if using). Mix well to combine.

Pour in chicken stock and heavy cream. Stir and bring to a gentle simmer. Nestle the seared pork medallions back into the sauce, cover, and simmer on low for 3–4 minutes, or until the pork is cooked through.

Taste and adjust seasoning with more salt and pepper if needed. Garnish with chopped parsley and serve over mashed potatoes or white rice.