Make the Romesco Sauce: Heat oil in an 8- to 10-inch heavy skillet over moderate heat until hot but not smoking, then add hazelnuts to skillet along with almonds, bread, garlic, and red pepper flakes and cook, stirring, until bread and garlic are golden, 2 to 3 minutes. Add chile powder and cook, stirring, until fragrant, about one minute longer.

Add tomatoes (with juiceto a food processor. Add bread and chile mixture, peppers, water, vinegar, and 1/4 teaspoon salt and purée until smooth. Thin with water if desired and season with salt.

Make the sandwiches: Cut the pieces of bread so that they have a top and bottom half. Spread the bottom pieces generously with Romesco Sauce. Then place two slices of cheese on the bottom half of each portion. Next, place two or three slices of the prosciutto onto each one. Sprinkle a few slices of scallion onto the prosciutto, then top with two slices of tomato each, then grind a little fresh pepper over all. Place two slices of the remaining cheese on top of the tomatoes. Top each sandwich with its top half of bread portion.

Grill the sandwiches: Use a medium setting on your panini grill since these are fairly thick sandwiches. Grill the sandwiches 4 to 5 minutes each, or until nicely toasted on their exteriors and they are fully heated, with melted cheese, inside.

Add salad: while the sandwiches grill, quickly toss together the salad ingredients in a medium bowl. Once the sandwiches are grilled, lift off their tops, place a generous handful of salad on them and replace their tops. Don’t worry if the tops don’t come off perfectly, they will all look a little different from each other. Place the sandwiches onto a platter or individual plates.

Serve the sandwiches immediately so they are still hot. Makes 6 large sandwiches.