Combine all the marinade ingredients in a large bowl or extra-large resealable plastic bag, adding the pork medallions last. Turn the meat in the marinade until well coated. Refrigerate for at least 3 hours. Heat deep fryer to 350°F. Fry spinach leaves until crispy; drain on paper towels. Lightly season with salt; set aside. Heat grill to medium-high heat. Remove pork from marinade (discard marinade); grill about 10 minutes, turning once, or until internal temperature is 155°F. Place on platter and keep warm. Meanwhile, place sweet and Yukon Gold potatoes in large saucepan; cover with salted water. Bring to a boil; simmer about 20 minutes or until potatoes are tender. Drain potatoes; place in standing mixer with whip attachment. Pour in cream. Add Boursin cheese, cinnamon, salt and pepper. Whip potatoes until smooth; keep warm. To finish pork medallions, top with blue cheese. Toss breadcrumbs with oil and Parmesan; sprinkle on top of blue cheese. Run under broiler to brown the crumbs, if desired.
NOTE: Boursin is a soft unripened French triple crème cheese. It has a rich, mild flavor that has been infused with garlic and herbs. Look for it in the deli section of larger supermarkets.
Spoon potatoes onto 12-inch plates. Arrange pork medallions next to potatoes and sprinkle spinach around the plate. Drizzle each plate with aged balsamic vinegar and extra-virgin olive oil, if desired.