In a skillet, cook the salmon fillet over medium heat for 10 minutes, about 5 minutes per side. Add a little salt and a pinch of ground black pepper. At the same time, in another pot, cook the chayotes cut in half for 20 minutes over medium-high heat with a pinch of salt. Cover completely with water. Once the chayotes and salmon are cooked, let them cool.

While the chayotes and salmon are cooking, prepare the mushroom sauce. In a pot, sauté 1 tablespoon of butter and 1/4 onion for 2 minutes over medium heat. Add the mushrooms with a pinch of salt and cook for 5 minutes or until the liquid has evaporated.

Next, add the garlic, oregano, rosemary, vinegar, and red wine. Let it reduce for 15 minutes. Then add the vegetable broth, ground black pepper, and salt to taste. Bring to a boil for 15 minutes. Add the butter, and to thicken, dissolve 1 tablespoon of cornstarch in cold water and add it until the sauce reaches your desired thickness.

Cover and reduce the heat to low. Cook for 20 minutes.

Once the chayotes are cool, carefully scoop out the flesh without breaking the shells. Chop the flesh into small pieces.

In a skillet, melt the butter and olive oil. Sauté the onion and garlic for 2 minutes. Add the flaked salmon, season with chicken bouillon powder and ground black pepper, and mix well. Add the chopped chayote flesh and salt to taste. Once cooked, let it cool.

In a bowl, mix the sour cream, half the cheese, and the egg. Stir well, then add the salmon and chayote mixture. Once combined, stuff the chayote shells with the mixture.

Place the stuffed chayotes in a baking dish greased with a little oil to prevent sticking. Top with the remaining cheese. Bake at 400°F (200°C) for 25 to 30 minutes or until golden and bubbly. Serve with the rice and mushroom sauce.