In a large mixing bowl, whisk together all-purpose flour and fine salt. Cut in the cold unsalted butter cubes until the mixture resembles coarse crumbs. Gradually add ice-cold water, mixing gently until the dough just comes together. Shape the dough into a rectangle, wrap tightly in plastic wrap, and refrigerate for at least 2 hours or overnight to ensure a flaky texture when baked.

Preheat your oven to 350°F (175°C) to toast the blanched slivered almonds. Spread the almonds on a baking sheet and toast for 8–10 minutes, or until golden brown and fragrant. Allow them to cool before grinding into a fine meal. In a saucepan, combine the ground almonds, granulated sugar, heavy cream, all-purpose flour, almond extract, vanilla extract, and a pinch of salt. Cook over medium heat for 5–7 minutes, stirring until the mixture thickens. Let it cool completely before using.

Once the dough has chilled, preheat your oven to 375°F (190°C). Roll out half of the dough on a floured surface into a rectangle measuring approximately 12x18 inches. Spread half of the cooled almond filling evenly, leaving a ½-inch border around the edges. Gently roll the dough like a jelly-roll into a horseshoe shape, tucking the ends slightly. Transfer the formed kringle to a parchment-lined baking sheet.

Place the assembled kringle in your preheated oven and bake for 25–35 minutes, until it turns golden brown and sounds hollow when tapped. Use an instant-read thermometer to check that the internal temperature reaches 200–210°F (93–99°C) for perfect doneness. Once baked, allow it to cool on the baking sheet for 10–15 minutes before carefully transferring to a wire rack to cool completely.

While the baked kringle cools, prepare the glaze by whisking together sifted powdered sugar, milk (or heavy cream), and the optional almond extract until smooth and glossy. Drizzle this delightful glaze over the cooled kringle, ensuring an even coating. If desired, sprinkle additional slivered almonds on top. Let the glaze set for 15–20 minutes before slicing and serving.