Bring plenty of salt water to the boil in a large pot. Remove 8 large leaves from the savoy cabbage. Wash the cabbage leaves and blanch in salted water for about 2 minutes. Lift out, quench and drain. Cut the middle ribs flat. Use the rest of the cabbage for other purposes.
Mix the couscous in a large bowl with broth and pour over 1⁄4 l boiling water. Let it swell according to the instructions on the packet.
Clean the mushrooms, wash if necessary and chop coarsely. Peel onions and garlic and chop finely. Wash thyme, shake dry, remove leaves and chop. Heat 1 tablespoon of oil in a large frying pan. Fry the mushrooms for about 5 minutes, turning them over. Fry the garlic, thyme and half the onion cubes briefly. Season with salt and pepper.
Grate gouda. Mix the mushrooms, cheese and pesto into the couscous. Season to taste with salt and pepper. Spread the mixture in the middle of the cabbage leaves, fold in the sides and roll the cabbage into roulades. Pin with wooden skewers.
Heat 3 tablespoons of oil in a large frying pan. Brown the roulades in it all around, take them out. Sauté the remaining onion cubes in the frying fat. Deglaze with wine and 200 ml water and bring to the boil. Stir in 1 teaspoon of stock and crème fraîche. Season to taste with salt and pepper. Put the roulades in the sauce and braise covered for about 15 minutes. Arrange roulades and sauce.