1. Sort and wash peas; place in a large Dutch oven. Cover with water to 2 inches above peas; cover and let stand 8 hours. Drain peas.
2. Heat a large saucepan over medium-high heat. Add 1 tablespoon oil; swirl. Add onion, celery root, and carrot; sauté 5 minutes or until onion begins to brown. Add peas, 3 cups water, and bay leaf; bring to a boil. Reduce heat, and simmer 1 hour and 15 minutes or until peas are tender. Discard bay leaf.
3. Heat a large Dutch oven over medium-high heat. Add remaining 1 tablespoon oil; swirl to coat. Add turnip; sauté 3 minutes or until edges begin to brown. Add garlic; sauté 1 minute. Stir in greens and 1/2 teaspoon kosher salt; sauté 1 minute. Add stock; stir until greens wilt. Cook 15 minutes or until greens are very tender. Remove from heat; stir in sugar and vinegar.
4. Preheat oven to 350°.
5. Lightly coat 6 (8-ounce) ramekins with cooking spray. Using a slotted spoon, spoon peas into prepared dish. Top evenly with greens mixture. Layer potatoes evenly over greens; sprinkle with 1/4 teaspoon salt and cheese. Drizzle with cream. Bake at 350° for 1 hour or until potatoes are tender and cheese is golden.