Get set up: Heat the oven to 425°F. Set out a sheet pan, a medium saucepan, a colander, and a large skillet so everything is ready.

Start the farro water: Fill the saucepan with about 3 quarts of water and bring it to a boil over high heat.

Season the vegetables: Put the Brussels sprouts on the sheet pan. Add 2 tablespoons of the olive oil, 1/2 teaspoon of the salt, and about 1/4 teaspoon of the black pepper, then toss to coat and spread them cut-side down in one layer.

Roast the Brussels sprouts: Slide the sheet pan into the oven and roast the Brussels sprouts for 10 minutes.

Cook the farro: When the water boils, add the farro and a generous pinch of salt to the saucepan. Stir once, lower the heat just enough to keep the water at a steady boil, and cook for 18 to 22 minutes, until the grains are tender with a little chew left in the center.

Finish roasting: Take the sheet pan out of the oven and turn the Brussels sprouts with a spatula. Return the pan to the oven and roast for 8 to 10 minutes more, until the leaves and cut sides are dark brown in spots and the centers are tender.

Toast the walnuts: Put the walnuts in the dry skillet and set it over medium heat. Stir for 2 to 3 minutes, until they smell nutty and look slightly darker, then transfer them to a small bowl.

Cook the shallot: Pour the remaining 1 tablespoon olive oil into the same skillet and keep it over medium heat. Add the shallot and a small pinch of salt, then cook for 2 to 3 minutes, stirring often, until softened.

Warm the beans: Add the black-eyed peas to the skillet with 1/3 cup water, the whole-grain mustard, half of the lemon zest, and 1 tablespoon of the lemon juice. Stir well and cook for 3 to 4 minutes, until the beans are hot and lightly coated in the mustard-lemon mixture.

Make the topping: Add the chopped parsley to the bowl of toasted walnuts and toss them together. Set the bowl aside for topping the finished bowls.

Drain the farro: Check the farro. When it is tender, pour it into the colander and let it drain well for about 30 seconds.

Season the farro: Transfer the drained farro back to the saucepan. Add the remaining lemon zest, the remaining lemon juice, 1/2 teaspoon salt, and the rest of the black pepper, then stir so the grains are evenly seasoned.