2tablespoonsolive oil, plus 1 tablespoon for greasing the pan
1/4cupoat flour
1/4cupsweet white rice flour
1/2teaspoonfine sea salt
6large eggs
3/4cupwhole milk
1/2cuphalf and half
4ouncesfresh goat cheese, crumbled (about 1 cup)
4ouncesgrated gruyère, or other nutty melting cheese such as Wagon Wheel(1 cup)
1bunch chives, chopped or snipped into 1/4" lengths
Instructions
Position a rack in the upper third of the oven and preheat to 350ºF.
Place the sliced potatoes in a small saucepan, cover with cool water, add a teaspoon of salt, and bring to a simmer. Cook the potatoes until tender, but not falling apart, about 10 minutes. Drain the potatoes and set aside. (You can save the water to use as stock in another recipe, if you like.)
Meanwhile, slice the green garlic and spring onions into 1/4" thick rounds. Place in a large bowl, fill with cool water, and separate the rings with your fingers. Let soak for a few minutes, swishing occasionally, to dislodge any sandy dirt that may be clinging between the rings.
Heat 2 tablespoons of the olive oil in a 10" oven-proof skillet over a medium flame until it shimmers. Scoop the green garlic and spring onions out of their soaking water, shake off any excess water, and saute until very tender, 10 minutes. Remove the garlic and onions to a bowl, wipe out the pan, and brush the bottom and sides with the remaining tablespoon of olive oil.
Meanwhile, whisk together the oat and rice flours with the 1/2 teaspoon of salt in a large bowl. Whisk in the eggs two at a time, whisking until smooth after each addition, then gradually whisk in the milk and half and half. Stir in the green garlic, spring onions, and chives, then fold in the cheeses, leaving the goat cheese in clumps.
Scatter the potatoes over the bottom of the oiled pan, then pour the batter over the top, taking care to distribute the solids evenly. Bake the quiche until puffed and golden all over the top, about 55 minutes. If you peek into the center, you should not see any wet batter. Let the quiche settle for at least 10 minutes, then cut into wedges and serve warm. Leftovers store well refrigerated airtight for up to three days; re-heat in an oven or toaster oven.