Flageolet Bean Gratin

This homey dish is warm and totally comforting - the perfect thing to bake when it's chilly outside and you need something to chase the cold away.  Like pretty much every recipe in Sunday Suppers at Lucques, it's fairly time and labor intensive, but the results are so worth it. Flageolet beans are simmered with rosemary, chile, and aromatics until they're tender and flavorful.  Then they're layered between sweet caramelized onions and a crunchy, buttery breadcrumb topping.  So good! 

This is a pretty rich dish, so I'd recommend pairing it with something acidic and/or bitter to cut the richness. I scooped up main-dish-sized portions alongside fennel-radicchio salad, but this could equally well work as a side dish alongside simple chicken or fish and a big green salad or steamed vegetables with lemon juice squeezed on top.  Note that despite the chile in the beans, this dish isn't at all spicy - if you want it that way, you should increase the amount of chile.

Flageolet Bean Gratin (adapted from Sunday Suppers at Lucques)
Serves 4-6 as a side or 2-3 as a main

Olive oil
1 small sprig rosemary
1/2 chile de arbol, crumbled
1/4 cup diced onion, plus 2-1/2 cups thinly sliced onions
1/4 cup diced fennel
2 small garlic cloves, peeled and smashed
1 T fresh thyme leaves, divided
1 bay leaf
3/4 cup dried flageolet beans, soaked in hot water for a few hours
2-1/2 T unsalted butter, divided
1 cup panko

1. Heat a medium pot over high heat for a couple of minutes.  Add a good glug of olive oil, and when it's hot, add the rosemary sprig and crumbled chile.  Let sizzle for about a minute, and then add the diced onion, fennel, garlic, 1/2 T thyme leaves, and bay leaf.  Stir for a minute or two, until the onion is softened.  Add the beans, and stir for a few minutes until the beans are coated in oil.
2. Cover the beans with water by about 3 inches, and bring to a boil over high heat.  Turn the heat down to low and keep the beans at a low simmer for half an hour.  Add 1-1/4 tsp salt, and simmer for a further 15 minutes or so, until the beans are completely tender.
3. While the beans cook, caramelize the sliced onions.  Heat a large non-stick skillet over high heat for a minute.  Add a good glug of olive oil to the skillet, and when it's hot, add the onion, remaining 1/2 T thyme leaves, 1/2 tsp salt, and a few grinds of black pepper.  Cook about 5 minutes, stirring often.  Turn the heat down to medium, and stir in 1/2 T butter.  Cook about 10 minutes, stirring often.  Turn the heat down to low, and stir for about 5 minutes until the onions are dark brown and caramelized.
4. Preheat the oven to 425 degrees.
5. Grease a 1-1/2 quart gratin dish with oil.  Spread the onions evenly over the bottom of the dish.  Spoon the beans over, along with a good amount of their liquid (the beans should be very moist but not swimming in liquid).
6. Heat the remaining 2 T butter in a small pan, and stir over medium heat until browned and nutty.  Stir in the panko until evenly moistened.  Sprinkle evenly over the beans.
7. Bake the gratin for 40-60 minutes, until browned and bubbling.  Let cool a few minutes before serving.