How to Make It
In a medium saucepan, cover the potatoes with cold water and season with salt. Bring to a boil, then simmer over moderate heat until the potatoes are tender, about 15 minutes. Drain and let cool, then cut into 1-inch pieces. Transfer the potatoes to a large bowl, add the mixed baby greens, bell pepper, scallions and capers and toss to combine.
Meanwhile, preheat the oven to 300°. Line a small baking sheet with foil. In a food processor, pulse the torn bread with the herbs until coarse crumbs form. Transfer to a small bowl. Stir in 2 tablespoons of the olive oil and the lemon zest and season with salt and pepper. Spread the crumbs on the baking sheet and bake for about 10 minutes, stirring occasionally, until they are golden and crisp. Let cool.
Heat the broiler to high. On a rimmed baking sheet, toss the squid with 2 tablespoons of the olive oil and season with salt and pepper. Broil 4 inches from the heat for 3 to 5 minutes, until the squid is opaque and just cooked through.
In a small bowl, whisk the lemon juice with the remaining 1/2 cup of olive oil and season with salt and pepper. Toss the salad with some of the vinaigrette. Transfer the salad to plates and top with the squid and herbed breadcrumbs. Serve immediately with the remaining vinaigrette alongside.