Preheat the oven to 300 F. In a medium mixing bowl, whisk together the whole egg, yolks, butter, sugar, salt, lemon juice and vanilla to combine. Pour the mixture into a measuring cup with a spout.
Spray a mini muffin pan or baking sheet with cooking spray, and place 1 frozen tart shell in each hole. Fill each shell to the top with the filling mixture. As you are pouring, whisk to recombine the ingredients as needed.
Bake until the tartlets puff up then deflate, about 15 to 18 minutes.
Remove the tartlets from the oven, and place on a wire cooling rack for 5 minutes; remove from the pan, and transfer to a serving platter to cool completely. Garnish each tartlet with a fresh raspberry or blueberry, and serve immediately.
Tips and Techniques:
*Phyllo shells are best used while still frozen.
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