How to Make It
Preheat the oven to 425°. Butter a 10-by-15 inch baking dish. Put the bread cubes on 2 large rimmed baking sheets and bake for about 10 minutes, until toasted. Let cool and transfer to a very large bowl.
Heat a large skillet. Working in batches, add the chard leaves by the handful and cook over moderately high heat, stirring, until wilted. Transfer to a colander set over a bowl and repeat with the remaining chard. When cool enough to handle, gently squeeze out the excess moisture from the chard and coarsely chop.
In the same skillet, heat the olive oil. Add the scallions and garlic and cook over moderate heat, stirring, until fragrant, about 2 minutes. Add the chard and peas and cook, stirring, until hot. Add the broth and cream and simmer over moderate heat until slightly thickened, about 3 minutes. Season with salt and pepper and let cool.
Add the chard mixture to the bread, season with salt and pepper and toss; transfer to the prepared baking dish. Scatter the blue cheese over the top and poke it into the pudding.
In a small bowl, combine the Parmigiano and 2 tablespoons of butter. Spread it over the pudding and bake in the upper third of the oven for about 15 minutes, until browned and crisp on top and hot throughout. Let the pudding rest for 10 minutes, then serve hot or warm.