Step 1Heat the oven to 325 degrees. Drop the almonds in a small pot of boiling water and leave for about 10 seconds. Drain, slide off the skins, and rub dry. Set aside.
Step 2Roast the hazelnuts on a small baking sheet until the skins darken and start to split, 10 to 15 minutes. While they are still hot, bundle them in a towel, then scrunch and massage them to rub off most of their skins. Pick out the nuts and set aside.
Step 3Turn the oven to broil. Spread the tomatoes one-half-inch thick in a small, shallow baking dish. Trickle with 1 teaspoon of the olive oil and broil until the tomatoes char slightly and bubble, a few minutes. Remove from the broiler.
Step 4Reduce the oven heat to 425 degrees. Meanwhile, pour a few cups of boiling water over the chile and leave to swell for a few minutes. Drain and then stem and seed the pepper.
Step 5Pour olive oil to a depth of one-half inch into an 8- or 10-inch skillet and set over medium-low heat. Test the temperature with the edge of the slice of bread; when it barely sizzles on contact, reduce the heat slightly and add the bread. (You may need to cut the bread into pieces so it fits into the pan in a single layer.) Check the underside at 1 minute; it should be beginning to color. Fry until it is the color of cornflakes, 2 to 3 minutes per side. Drain and cool on a paper towel.
Step 6Thickly slice the garlic, then pound to a paste in a mortar. Scrape into a processor and add the chile, fried bread, almonds and hazelnuts. Grind to a fine, moist paste, scraping the sides frequently. Scrape in the tomato and process to a paste. Add the vinegar, paprika, the remaining extra-virgin olive oil and salt to taste. Taste; it should be bursting with flavor, although not overly spicy. The flavor of the paprika will come out over time.
Step 7Spread the paste in a thick layer in a small, shallow baking dish and bake until the surface has turned dark orange with occasional flecks of brown, about 8 minutes. (Makes about 1 cup. Can be made up to a week in advance.)
Step 1Bring the stock, fumet or water and the white wine to a simmer in a small saucepan. Turn off the heat and stir in the romesco base. Taste for salt. Cover and set aside for about 30 minutes. As this brew cools, the crumbs will begin to swell and soften, which will give the sauce a nice texture.
Step 2Place the diced onions in a 3-quart saute pan with about 2 tablespoons of the olive oil and a few pinches of salt. Cook over medium heat until translucent and tender, about 5 minutes. Add the romesco and warm through, about 1 minute. Add the shrimp and turn the heat to medium-low. Cook gently, turning each one over once in the thickening sauce, until the shrimp are just firm and opaque, about 4 minutes, depending on the size of the shrimp.
Step 3Meanwhile, warm another 2 tablespoons olive oil in a 12-inch skillet over medium heat. Add the spinach and sprinkle with salt. Gently turn and fold leaves until they are uniformly wilted and bright green. Taste for salt and add another trickle of oil if the spinach seems lean.
Step 4Divide the spinach among warm plates. Arrange the shrimp on top. Taste the sauce, and correct the salt. The romesco should be fluid but thick; reduce briefly or add a splash of water if it seems either watery or pasty. Spoon the sauce over all.