Heat oven to 375 and line a baking sheet with parchment
Thinly slice the sweet potato, then in a mixing bowl, toss it with 1 tablespoon of olive oil to coat. Sprinkle in the rosemary, sprinkle with sea salt and mix well again
Spread onto the lined sheet and roast for 20 minutes. Flip them over and roast for another 5 minutes. Remove from the oven and set aside. Turn the oven up to 400
In a small saucepan over medium-low heat, melt together the butter and 1/2 tbsp. olive oil. Stir in the garlic and sauté until softened, about 1-2 minutes. Keep stirring to keep from burning. Add in the spinach and stir well. Cook over medium low for another 2-3 minutes until wilted. Remove form heat and set aside
Grease a 9x9 dish and layer the potatoes evenly on the bottom. Cover them evenly with the spinach and set aside
In a large mixing bowl, whisk together the eggs and milk, then pour over the potatoes and spinach. Sprinkle it with the shredded cheese
Bake for 25 minutes until the centre is set. Turn the broiler to high and broil for 2 minutes to crisp up the top
Let sit for 5 minutes before slicing
Garnish with sliced green onions