Heat the oven to 400 degrees. Place the flour, 1/4 cup powdered sugar and salt in food processor. Process the mixture for 10 seconds. Add the butter, cut into chunks. Process until the mixture is crumbly. Add the egg yolk. Process until mixture holds together. Scoop the dough into a 9-inch tart pan with a removable bottom. With floured fingers, press the dough evenly in the bottom and up the sides of the pan. Bake for 12 to 13 minutes or until golden brown. Remove from the oven. Set aside to cool. Meanwhile, combine the cream cheese, milk and pudding mix in mixer bowl. Beat with an electric mixer on medium speed until creamy. Add the sour cream. Beat at medium speed until thick and creamy. Spoon and spread evenly in the slightly warm tart shell. Cover; refrigerate for 20 minutes. Place the thawed strawberries in a food processor. Process until pureed. Pour the puree in a wire mesh strainer over a medium bowl. Press through the sieve, removing the seeds. You should have about 3/4 cup of puree. Combine the puree, 1/4 cup powdered sugar and cornstarch in a small saucepan. Whisk until smooth, cooking over medium heat until the mixture boils. Lower the heat and simmer for 1 minute. Set aside to cool. When the puree is room temperature, remove the tart from the refrigerator. Top the tart with fresh strawberries and spoon/spread the puree over the berries. Return to refrigerator for 10 to 20 minutes or until chilled (or up to 8 hours). If desired, just before serving, sprinkle with 2 tablespoons of powdered sugar and garnish with fresh mint leaves. Tip: If pressed for time, use a refrigerated pie crust for the tart shell. Bake as directed on the package.