Cheddar Chive Red Potato Breakfast Gratin

Steps

1. Preheat the oven to 375°F (190°C). Grease an 8x8-inch baking dish with the butter.
2. Shred the cheddar and split it into two halves. Slice the green onion and set aside one-third for garnish; the other two-thirds go in the bake.
3. In a bowl, whisk the eggs, milk, garlic, thyme, salt and black pepper to make the custard.
4. Arrange one-third of the potato slices in the dish, overlapping. Scatter over half the spinach, half of the in-bake green onion and half of the first cheddar half (one-quarter of the cheddar).
5. Add another third of the potatoes, then the remaining spinach, the remaining in-bake green onion and the rest of the first cheddar half. Top with the final third of the potatoes.
6. Pour the custard evenly over the potatoes, pressing the layers down so they are mostly submerged.
7. Cover tightly with foil and bake 45 minutes, until a knife slides easily through the potatoes.
8. Uncover, sprinkle the second half of the cheddar and the Parmesan over the top, and bake 20 to 25 minutes more, until golden and the custard is set and reaches 160°F (71°C) in the center.
9. Rest 10 minutes, then sprinkle with the reserved green onion, cut into 4 portions and serve.