Heat the olive oil in a large sautÈ pan over medium heat. Add the onions, season with salt and pepper, and cook, stirring, for 1 minute. Add the duck confit and cook, stirring for 1 minute. Season with salt and pepper. Add the tamarind sauce and cook, stirring, for 2 minutes. Season again with salt and pepper. Stir in the green onions and remove from the heat.
In a large, heavy, deep pot or electric fryer, heat 4 inches of vegetable oil to 360?F. Fry the tortillas, a couple at a time, until golden brown, about 2 minutes. Drain on paper towels. Season with salt and pepper.
In a small mixing bowl. Combine the sour cream, lemon juice, and cilantro and whisk to blend. Season with salt and pepper. In another small mixing bowl, combine the avocados, lime juice, garlic, and 2 tablespoons of the tomatoes. Season with salt and pepper. Stir to mix.
To assemble, lay 1 tortilla in the center of each plate. Place 1/2 cup of the duck mixture on top of each tortilla. Top the duck mixture with the shredded lettuce, the tomatoes, and cheese. Top with a second tortilla and repeat with the confit, lettuce, tomatoes, and cheese. Top with the remaining tortillas. Garnish with the cilantro sour cream and the avocado mixture.
Yield: 4 servings