Preheat the oven to 400?F.
Roll out the piecrust on a lightly floured surface to fit a deep 9-inch pie pan. Place the pastry in the pie pan and crimp the edges decoratively. Refrigerate the pastry for at least 30 minutes, then line with aluminum foil. Fill with pie weights and bake for 12 to 15 minutes, or until lightly golden around the edges. Remove the foil and pie weights and return the crust to the oven for 3 to 5 minutes. Remove from the oven and brush the surface of the piecrust with a light coating of egg white; allow to cool.
In a large skillet, melt the butter over medium-high heat. Add the onions, bell peppers, and Essence and cook until the vegetables soften, about 4 minutes. Add the green onions and garlic and cook for 1 minute. Add the crawfish tails with their fat, tasso, and tomato paste and cook for 2 minutes longer. Transfer to a bowl and let cool. Once cool, stir in the cheese.
In a large bowl, whisk together the eggs, half-and-half, thyme, salt, black pepper, and cayenne. Pour the crawfish mixture into the pie shell, and pour the egg mixture over the top. Bake on the bottom rack of the oven until the custard is set and the quiche is golden brown on top, about 30 minutes. Allow to cool slightly before serving.
Makes one 9-inch quiche, about 8 servings