In a saucepan, add one drizzle of olive oil, the unsalted butter, stir until melted.
Add the onion chopped into small cubes, the leek chopped into round slices, the red bell pepper chopped into small cubes, stir-fry for 2 minutes.
Add the grated carrot and the red chili pepper chopped into round slices, stir-fry for 2 minutes.
After this indicated time, add the potatoes chopped into cubes, add the water, stir, cover the saucepan and let it all cook for 15 minutes.
Meanwhile, in a skillet, add a generous drizzle of olive oil, add the mushrooms cut in half, the minced garlic cloves, stir-fry until golden brown.
Now, in another skillet, add one drizzle of olive oil, add the tuna steaks, fry on each side for 2 minutes.
Next, in the saucepan with the soup, add the mushrooms, the tuna steaks and season with the salt, the black pepper and the dried basil, stir well.
Cover the saucepan and let it all cook for 15 minutes.
After this indicated time, pour in the mixture made with the table cream and the egg yolk, stir well and let it all cook for another 15 minutes.
Finish with parsley to taste.
Serve.