How to Make It
Preheat the oven to 400°. In a large saucepan, heat the oil. Add the onion, garlic and a generous pinch of salt and cook over moderate heat, stirring occasionally, until the onion begins to soften, 3 to 5 minutes. Add the sorghum and stock and bring to a boil over high heat. Reduce the heat to low, cover and simmer, stirring occasionally, until the sorghum is tender and the stock is absorbed, about 1 hour. Season the sorghum with salt and pepper.
In a very large bowl, toss all of the vegetables with the olive oil and season generously with salt and pepper. Spread the vegetables in an even layer on 2 large rimmed baking sheets. Roast until tender and lightly browned, 30 to 35 minutes; stir the vegetables halfway through roasting.
In a medium saucepan, melt the butter. Add the onion and cook over moderate heat, stirring occasionally, until just softened, about 5 minutes. Add the parsnips, stock and a generous pinch of salt and bring to a boil. Simmer over moderately high heat until the parsnips are tender and the stock is slightly reduced, about 20 minutes. Let cool slightly, then transfer the parsnips and their cooking liquid to a food processor and puree until smooth. Season with salt.
Fold the cooked sorghum into the parsnip puree and spread evenly in a 9-by-13-inch or 4-quart baking dish that’s at least 2 inches deep. Scatter the roasted vegetables evenly over the puree. Cover with foil and bake for about 25 minutes, until bubbling.
In a large saucepan, heat 1/2 inch of oil until shimmering. In a bowl, toss the sliced shallots with the flour. Working in batches, fry the shallots over moderately high heat, stirring, until lightly browned and crisp. Using a slotted spoon, transfer the fried shallots to a paper towel–lined plate to drain; season with salt. Garnish the casserole with the crispy shallots and chives and serve.
Sorghum is a grain that grows in the Midwest and the South. If you can’t find pearled sorghum, use unpearled (whole) sorghum. Soak the grain overnight and increase the cooking time to about 1 hour and 45 minutes.