Peas are made up of starch and fiber. When they are split, then cooked, the pea solids have no "shell" to hold them together. They disperse into the cooking liquid. Depending on how much liquid is available, the will either distribute evenly, or settle to the bottom of the broth. Adding a roux to your split pea soup sill dilute the sometimes strong flavor, and extend the soup. It also binds the pea solids in suspension. I like strong flavors and so use a little less water. The pea solids stay suspended evenly. I balance the flavor with onion, carrot, salt, and garlic. I often add a ham bone, smoked pork hocks, or ham to the soup to give it a smokey flavor, plus the flavor of the ham.
Dried whole peas will soften into an edible pea. it will not taste like fresh peas. It won't be sweet, but a little bitter and savory. The flavor will be identical to split peas.
pearl barley will give you the texture you're looking for, as will rice, wild rice, groats, and some kinds of pasta, especially orzo. Their are other grains as well. I know there are people here that have experimented with many of them.
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