Season the pork medallions with kosher salt, black pepper, and garlic powder on both sides.
Heat olive oil in a large skillet over medium-high heat.
Add the pork medallions to the skillet and cook for 3-4 minutes per side until golden brown and cooked through. Transfer to a plate and cover to keep warm.
In the same skillet, add butter, shallots, and garlic. Sauté for about 1 minute until fragrant.
Add the sliced mushrooms and cook for 4-5 minutes until softened and browned.
Pour in white wine, stirring to deglaze the skillet and scrape up any browned bits.
Stir in heavy cream, thyme leaves, and balsamic vinegar. Simmer for 2-3 minutes until the sauce thickens slightly.
Return the pork medallions to the skillet, spoon the sauce over them, and cook for another 1-2 minutes.
Garnish with chopped parsley and serve hot.