How to Make It
Lightly brush the bell pepper with olive oil and roast it directly over a gas flame or under the broiler, turning frequently, until charred all over. Transfer to a bowl, cover with plastic wrap and let stand for 15 minutes. Peel, core and seed the pepper and cut it into thick strips.
Meanwhile, in a medium skillet, heat 1 tablespoon of the olive oil until shimmering. Add the almonds and cook over moderate heat, stirring constantly, until golden, about 5 minutes. Transfer to a cutting board and let cool slightly, then coarsely chop.
Heat 1 tablespoon of the olive oil in the skillet. Add the bread cubes and cook over moderate heat, stirring frequently, until golden and crisp, about 5 minutes. Transfer to a plate. Heat another tablespoon of the olive oil in the skillet. Add the bell pepper strips and garlic and cook, stirring occasionally, until the garlic is lightly golden and softened, about 5 minutes. Add the tomatoes and cook for 1 minute longer. Transfer to a large mortar or food processor and let cool.
Add the fried almonds to the bell pepper mixture and using a pestle, pound to a coarse paste, or pulse in the processor. Add the toasted bread cubes and 1 tablespoon of the olive oil, then pound and stir, or pulse, until the sauce is emulsified. Gradually add 1/4 cup of olive oil, stirring and pounding, or pulsing, until emulsified. Stir in 2 tablespoons of the sherry vinegar and season with salt and cayenne.
In a large deep skillet, heat the remaining 2 tablespoons of extra-virgin olive oil until shimmering. Add the leeks and cook over moderate heat, turning occasionally, until lightly browned and barely softened, about 10 minutes. Add the chicken stock and the remaining 1 tablespoon of sherry vinegar, season with salt and cayenne and bring to a boil. Cover the leeks and cook over moderate heat until tender, 10 to 12 minutes longer. Let the leeks cool, then drain.
Arrange the braised leeks on a large platter. Spoon half of the romesco sauce over the leeks. Sprinkle the crumbled Garrotxa cheese on top and serve with crusty bread and the remaining romesco on the side.