Cook the barley: Fill a medium saucepan with plenty of water, add a generous pinch of salt, and bring it to a boil over high heat.

Add the pearl barley to the boiling water and stir once so it does not stick to the bottom of the saucepan.

Lower the heat to keep the water at a steady simmer and cook the barley for 28 to 32 minutes, until it is tender but still pleasantly chewy.

Set a colander in the sink. Drain the barley, reserving 1/2 cup of the cooking water, then return the drained barley to the empty saucepan off the heat.

Build the bean topping: While the barley cooks, heat the olive oil in a large skillet over medium heat.

Add the chopped onion and the scallion whites to the skillet with 1/2 teaspoon of the salt. Cook for 5 to 6 minutes, stirring now and then, until the onion is soft and lightly golden.

Add the sliced garlic and smoked paprika to the skillet. Stir for about 30 seconds, just until the garlic smells fragrant.

Add the black-eyed peas and 1/2 cup water to the skillet. Stir well and bring the mixture to a gentle simmer.

Cook the beans for 3 to 4 minutes, until they are hot all the way through. Use the back of a spoon to lightly mash some of the beans in the skillet so the mixture turns a little thicker and saucier.

Add half of the mustard greens to the skillet and stir until they start to wilt. Add the remaining greens and keep stirring for 2 to 3 minutes, until all the greens are softened and mixed into the beans.

Stir the apple cider vinegar and the remaining 1 teaspoon salt into the skillet. Add the black pepper, taste, and adjust with a little more salt if needed. Keep the skillet over low heat while you finish the barley.

Finish the bowls: Add 3 ounces of the grated cheddar and 1/4 cup of the reserved barley cooking water to the saucepan with the drained barley.