Preheat oven to 375˚F.
For mashed sweet potatoes: Place potatoes into a medium pot, fill with water and bring to a boil. Boil potatoes until fork tender, about 15 minutes. Drain potatoes into a colander and return back to the pot. Add butter, season with salt and pepper and mash with a potato masher, until smooth and creamy. Fold in the Havarti until just combined and adjust seasonings. Cover and set aside.
For filling: Pour 1 tablespoon oil into a large skillet and place over medium-high heat. Add ground lamb and season with salt and pepper. Sauté lamb for 4 to 5 minutes or until just browned. Transfer meat into a mixing bowl and drain excess liquid and grease.
Pour remaining oil into the skillet and sauté turnip over medium-high heat for 4 to 5 minutes. Add shallots and garlic and continue to sauté for 2 minutes. Season with salt and pepper.
Return ground lamb to the skillet with herbs and tomato paste and stir mixture together. Until well combined.
Lower heat to medium-low and sprinkle flour over mixture and continue to stir together. Add vegetable stock, stir and allow mixture to slightly thicken. Fold in corn and peas and adjust seasonings.
To assemble: Whisk egg into the mashed and slightly cooled sweet potatoes until fully combined and mixture is light and creamy. Pour filling into a 9”x13” baking dish, in an even layer. Top with mashed sweet potatoes, smooth the top and bake for 25 to 30 minutes.
Place pie under broiler for 3 to 4 minutes or until lightly browned. Allow Shepard’s pie to cool for 10 minutes before serving.