Molly Gilbert, I'd like to personally thank you for writing Sheet Pan Suppers. Living in a studio by myself, it can be a challenge to muster up the strength to cook for one . . . and do all the dishes by hand. But your cookbook is a game changer. First of all, it's better than one-pot cooking, which is fancy talk for steaming everything together. Roasting food on a sheet pan allows for amazing caramelization. And second of all, can we talk about the beans in this stuffed sweet potato recipe? They are so perfectly seasoned. Who knew capers, golden raisins, and herbes de Provence are the flavor trifecta for beans? I'm looking forward to cracking the spine of my Sheet Pan Suppers and staining many a page with oil and other food remnants, because everyone knows that a well-loved cookbook is well-worn.
Preheat the oven to 400°F with a rack in the center position. Line a sheet pan with aluminum foil or parchment paper.
Place the sweet potatoes on the prepared sheet pan and bake until soft enough to pierce easily with a paring knife, about 1 hour. Set aside on the sheet pan to cool to the touch.
Meanwhile, stir together the beans, capers, raisins, lemon juice, herbes de Provence, salt, pepper, red pepper flakes, and 1 teaspoon of the olive oil in a medium-size bowl.
When the sweet potatoes are cool enough to handle, use a paring knife to split each one open lengthwise, taking care not to cut all the way through. (We're going to fill them like loaded baked potatoes.) Gently press the short ends of each potato together to expose the soft flesh and create a nice crater for the filling.
Use a spoon to distribute the bean mixture among the potatoes. Toss the spinach with the remaining tablespoon olive oil in the same bowl you used for the beans. (The bowl will have some delicious "dressing" still clinging to it.)
Stuff a big handful of spinach (about 1 cup) inside and on top of each bean-filled potato (they'll be overfilled and the spinach will overflow onto the baking sheet — that's OK).
Return the sheet pan to the oven and bake the potatoes until the spinach has wilted and everything is warmed through, 5 to 10 minutes. Serve the loaded potatoes hot from the oven.