Rinse the rice in a fine-mesh strainer under cold water until the water runs mostly clear, then shake it dry and leave it to drain while you prep everything else.

Combine the lentils and 1 1/2 cups water in a small saucepan. Bring them to a boil, then lower the heat and simmer for 15 to 18 minutes, until the lentils are tender but still hold their shape. Drain them and set aside.

Stir the spice blend ingredients together in a small bowl. It makes about 3 1/2 tablespoons, and you will use 2 tablespoons in the pot.

Heat 2 tablespoons of the olive oil in a large Dutch oven or heavy pot over medium-high heat. Add the mushrooms in a single layer and leave them alone for 4 minutes, until the liquid they release has cooked off and the undersides are browned. Add the walnuts and toast for 1 minute more, then scrape everything onto a plate.

Add the remaining oil to the pot and lower the heat to medium. Cook the onion, bell pepper, and celery with a pinch of salt for 5 minutes, until they soften. Stir in the garlic and cook for 30 seconds, then add 2 tablespoons of the spice blend and stir for 30 seconds, until it smells toasted.

Add the drained rice and stir for 2 minutes, until the grains look glossy and the edges turn translucent. Pour in the broth and soy sauce, scrape the bottom of the pot, and bring it to a boil. Cover, turn the heat to low, and cook for 15 minutes without lifting the lid.

Take the pot off the heat, scatter the lentils, mushrooms, and walnuts over the rice without stirring, and put the lid back on for 10 minutes. Fork the rice through, season with salt and more of the spice blend, and serve with scallions, parsley, and hot sauce.