Peel the onion, carrot, and celery and cut them in half. Peel the potatoes and cut them into cubes. Wash the bones and put them in a large pot.
Add water, bay leaves, and chopped vegetables. When it starts to boil, remove the foam that has accumulated on it with a strainer.
Cook for 20 minutes, till the vegetables are softened.
Remove the vegetables from the pot and drain, but keep the water in it. Then, add the potatoes to this water. Whisk with a mixer until you get a smooth consistency.
Melt the butter in a separate pot and roast the flour. Add the mashed potatoes little by little and boil for about 10 minutes. Remove it from the stove.
For the topping, melt the butter and roast the mint and red pepper powder. Divide the soup into serving bowls. Place the crusty bread on top of each bowl.
Pour the butter-roasted spice mixture over the soup. Serve hot.