Cut out the core off the cabbage and chop the rest of the cabbage into tiny little pieces. Add the finely chopped cabbage into a large bowl of boiling water and let it sit for 2 minutes. Then, strain the water and rinse with cold water so that the cabbage stops cooking.
Rinse the rice a few times and place it in a saucepan. Add enough water so that there is about 4 inches of water above the rice. Bring the rice to a boil and cook on medium high heat for 11 minutes. Once the rice is about 90 percent done, strain the water and set aside.
In a skillet heat oil to medium high heat and cook 1/2 cup chopped onion and 2 shredded carrots. Cook until the onion becomes translucent.
In a large bowl mix the ground chicken, cabbage, rice, salt and pepper, with the sautéed onion and carrot. I find it easiest to just mix it with my hands.
Using a cookie scoop, scrape out balls of the mixture. Make sure each scoop is very full. Round each ball in your hands so that its more compact. In a 9x13 baking dish tightly place the cabbage rolls.
Preheat your oven to 370 degrees F.
In a skillet heat 3 tbsp olive oil and sauté rest of the onion and carrots. Once the onion is translucent add in the sour cream and tomato sauce. After about 5 minutes, stir in 1/2 cup water.
Spread the sautéed mixture over the cabbage rolls, cover with foil, and bake for 1 hour.