Heat butter in a large saucepan over medium low heat.
Add garlic and cook around a minute until golden. Then, add onion and sugar, cooking 15-20 minutes until caramelized.
Pour both types of rice and 4 cups chicken stock into the pot. Bring to a boil and then simmer 20 minutes.
Add lentils and 2 more cups of stock. Let simmer for 20-25 more minutes until the rice and lentils are fully cooked and stock is evaporated. You can add in extra water by the half cup if you lentils dry up too soon. Add salt and pepper to taste.