In a large pot, add oil and sauté crab shells until fragrant, about 5 minutes.

Add chopped celery, onion, parsley stems, peppercorns, and bay leaves. Sauté for another 5 minutes.

Add tomato paste and continue to sauté until the tomato paste turns a bit darker than its original color.

Deglaze with white wine. Once the wine is reduced to about 1/2 cup, add 12 cups of cold water.

Bring to a boil, then reduce to a simmer for 45 minutes. Do not cook longer than 1 hour. Strain the stock.

In a separate pot, heat butter and sauté diced onions until translucent.

Add rice and stir to coat with butter.

Pour in white wine and cook until the wine is absorbed.

Gradually add crab stock, one ladle at a time, stirring constantly until the liquid is absorbed before adding more.

Continue until the rice is creamy and cooked to your desired texture.

Stir in crab meat, Swiss cheese, Gruyère cheese, and chopped parsley. Season to taste.