First, prepare the leaves.
Remove the stems from the big leaves and cut them in two. Use only tender and small pieces for rolling and try to keep them all of the same size. Set aside.
To prepare the stuffing:
In a large pot on medium heat, add the oil and onions. Sautee until translucent.
Add the rice and continue to cook for about 5 minutes, stirring.
Add the mushrooms.
Cook, stirring from time to time, for about 10 minutes or until the rice absorbs the liquids.
Turn off the heat, add the carrots, ½ of the tomato paste, ½ of the chopped dill, dry dill, thyme, salt, and pepper. Stir to combine. Let cool.
To stuff the rolls:
Put a Tbsp of the stuffing mixture on a leaf.
Cover the filling with the edge from the base of the leaf. Bend the edges on both sides and cover over the filling.
Roll the stuffed cabbage leaf while holding it firmly, so it won't break during cooking time.
Repeat these steps until you finish all of your mixture.
In a large pot, place the very big leaves of the cabbage (that you could not use for the rolls) to cover the bottom. Arrange the rolls evenly on the bottom in 2 layers.
Cover the layers with another layer of cabbage rolls, one part of the tomato paste, part of dill and repeat with the rest of rolls.
To cover the last layer, use the rest of the cabbage leaves, peppercorns, and the bay leaves.
Add boiling water until it nearly reaches the last layer of rolls.
When the water in the pot starts to boil, turn the heat to low and cover the pot. Cook for about 2 hours.
Make sure to check from time to time the level of water. If it was absorbed, add about a cup each time.
Serve warm, with polenta on a side, with chopped fresh herbs or vegan cream.