01 - Heat olive oil in a large pot over medium heat. Add the diced onion, sliced carrots, sliced celery, and minced garlic. Cook, stirring occasionally, until the vegetables have softened, about 5 minutes.
02 - Add the rinsed lentils, diced tomatoes with their juice, vegetable broth, bay leaf, dried thyme, smoked paprika, salt, and pepper. Bring to a boil, then reduce the heat to low. Cover and simmer for 25–30 minutes until the lentils are tender. Remove and discard the bay leaf.
03 - While the stew simmers, whisk together the flour, baking powder, and salt in a mixing bowl. Cut in the cold butter using your fingertips until the mixture resembles coarse crumbs. Pour in the milk and stir gently until just combined — avoid overmixing.
04 - Increase the heat under the pot so the stew returns to a lively simmer. Drop rounded tablespoonfuls of dumpling dough onto the surface of the stew, spacing them apart (yields 8–10 dumplings). Cover the pot tightly and steam for 15 minutes without lifting the lid, until the dumplings are puffed and cooked through.
05 - Taste the stew and adjust the seasoning with additional salt and pepper as needed. Sprinkle with chopped fresh parsley before serving, if desired.