3/4 cup freshly grated Parmigiano-Reggiano cheese (2 1/2 ounces)
Salt and freshly ground pepper
Preheat the oven to 350°. Butter a 1-quart soufflé dish or deep baking dish. Add 2 tablespoons of the bread crumbs and shake the crumbs around the inside of the dish to coat it completely.
Heat a large skillet. Add the Swiss chard in 2 batches and cook over moderately high heat, stirring, until wilted. Transfer to a colander and rinse under cold running water; squeeze dry. Transfer the chard to a food processor and pulse until very finely chopped.
In a small saucepan, heat the milk until bubbles appear around the edge. In a medium saucepan, melt the butter over moderate heat. Add the remaining bread crumbs and stir to coat. Gradually pour in the milk, stirring, until the mixture is thick. Remove from the heat and stir in the chard and the cheese. Season with salt and pepper and scrape the mixture into the prepared dish.
Bake the sformatino for about 30 minutes, or until set. Invert the sformatino onto a large plate and cut it into 8 wedges. Serve hot, alongside the beef.