1. Begin by mixing the all-purpose flour, granulated sugar, and salt in a large bowl. Cut in the cold, cubed butter until the mixture resembles coarse crumbs. Stir in the sour cream until a soft dough forms. Shape the dough into a ball, wrap it in plastic, and chill it for at least 1 hour.

2. While the dough is chilling, prepare the apple filling. In a pan, combine the diced apples, brown sugar, cinnamon, nutmeg, and lemon juice. Cook over medium heat for 5-7 minutes, stirring occasionally, until the apples are tender and the mixture has thickened slightly. Allow the filling to cool completely before assembling the kringle.

3. On a lightly floured surface, roll the chilled dough into a large rectangle. Spread the cooled apple filling down the center of the dough, leaving space on the edges. Fold both sides of the dough over the filling, pinching the seams to seal. Carefully transfer the shaped kringle to a parchment-lined baking sheet, forming it into an oval or horseshoe shape.

4. Preheat your oven to 375°F and bake the Wisconsin Apple Kringle for 25-30 minutes, or until the crust is golden brown. Allow the pastry to cool slightly before preparing the glaze.

5. In a small bowl, whisk together the powdered sugar, milk, and vanilla extract until a smooth glaze forms. Drizzle the warm glaze over the Wisconsin Apple Kringle, allowing it to drip down the sides and create a beautiful, shiny finish.