Rinse the lentils and soak them in a bowl of hot water for 30 minutes.
While the lentils are soaking, grate the ginger and place it in the bowl of a food processor.
In a second bowl, combine the diced onion, chopped cilantro, minced pepper, and spices.
When the lentils are done soaking, puree them in the food processor with the ginger until a thick paste forms. [You may need to pause and scrape the bowl down.]
Stir the lentils into the onion mixture until a wet dough forms.
Shape into balls, roughly the size of a golf ball.
Chill for 30 minutes in the freezer.
Mix the yoghurt, dill, garlic, and spices in a small bowl until combined.
If raita is too thick for your tastes, you can add a splash of lemon juice or vinegar.
In your smallest pot, heat 1 1/2 -2 cups of vegetable oil. To test temperature, throw in a crumb. If it sizzles, the oil is ready.
Fry the piaju one or two at a time being careful to keep the oil temperature high.
Let piaju drain on a paper towel.
Serve warm with raita for dipping.