01 - Heat olive oil in a large heavy-bottomed pot over medium heat. Add the diced onion, carrots, and celery. Cook for 5 to 7 minutes, stirring occasionally, until the vegetables have softened and the onion turns translucent.
02 - Stir in the minced garlic, dried thyme, smoked paprika, and tomato paste. Continue cooking for 2 minutes, stirring constantly, until fragrant and the tomato paste darkens slightly.
03 - Add the rinsed lentils and bay leaf to the pot. Pour in the vegetable broth and stir to combine. Bring the mixture to a rolling boil, then reduce the heat to low. Cover the pot and let it simmer for 25 to 30 minutes, or until the lentils are tender. Season with salt and pepper to taste.
04 - While the lentils simmer, whisk together the flour, baking powder, salt, and dried herbs in a medium mixing bowl. Add the cubed cold butter and cut it in using your fingers or a pastry blender until the mixture resembles coarse crumbs. Pour in the milk and stir gently until a soft, slightly sticky dough forms.
05 - Remove and discard the bay leaf from the lentil mixture. Drop rounded tablespoonfuls of the dumpling dough evenly over the surface of the simmering stew. Cover the pot tightly and steam over low heat for 15 minutes. Resist the urge to lift the lid during this time, as the steam is essential for proper cooking.
06 - Check that the dumplings have puffed up and are cooked through. Ladle the stew into bowls, distributing the dumplings evenly. Serve hot, garnished with fresh parsley and a squeeze of lemon juice if desired.