In a large mixing bowl, whisk together all-purpose flour and fine table salt. Using a pastry cutter or two forks, cut in the cold unsalted butter until the mixture resembles coarse crumbs, with pea-sized butter pieces. Gradually add ice-cold water, mixing until the dough just comes together. Shape it into a rectangle, wrap in plastic, and refrigerate for at least 2 hours or overnight for optimal flakiness.

Preheat your oven to 350°F and spread the blanched slivered almonds on a baking sheet. Toast them for 8-10 minutes, watching closely for a golden color, then cool and finely grind them in a food processor. In a medium 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 while stirring constantly until thickened, about 5-7 minutes, and allow it to cool completely.

Preheat your oven to 375°F and line a baking sheet with parchment paper. Divide the chilled dough in half and roll each piece into a 12x18-inch rectangle on a floured surface. Spread half of the cooled almond filling evenly on each rectangle, leaving a ½-inch border. Carefully roll up each dough rectangle like a jelly roll, shaping it into a horseshoe. Place both kringles on the prepared baking sheet and bake for 25-35 minutes, until golden brown and reaching an internal temperature of 200-210°F. Allow them to cool for 10-15 minutes on the baking sheet before transferring to a wire rack.

In a small bowl, whisk together powdered sugar, milk or heavy cream, and the optional almond extract until you achieve a smooth glaze consistency. Drizzle the glaze generously over the cooled almond kringles, allowing it to cascade down the sides. For an extra touch, garnish with slivered almonds and let them set for 15-20 minutes before slicing and serving your delightful Almond Kringle.