Dough:

In the bowl of a stand mixer, combine the flour, sugar, and salt. Add the butter and mix until incorporated. Add the egg yolks and wine and mix until a dough forms. Replace the paddle with a dough hook and knead dough on medium speed until smooth, 5-6 minutes. Form dough into a ball and wrap in plastic; set aside to rest for 30 minutes.

Poppy seed Fillings:

Heat the apricots, poppy seeds, 1⁄2 cup wine, 1⁄2 cup sugar, and 1⁄3 cup jam over medium heat and cook, stirring, until hot, 4 minutes. Transfer the poppy seed filling to a small bowl; set aside.

Apple Filling:

Heat the remaining jam, cinnamon, cloves, and apples in a small saucepan over medium-high heat and cook, stirring, until apples soften, 8-10 minutes. Transfer the apple filling to a small bowl; set aside.

Walnut Filling:

Heat the remaining wine, 6 tbsp. sugar, walnuts, and chocolate over medium heat and cook, stirring, until smooth, 2-3 minutes. Transfer the walnut filling to a small bowl; set aside. Heat the prunes and 1 1⁄2 cups water in a small saucepan over medium-high heat and cook, stirring, until the prunes are soft and water is almost evaporated 16-18 minutes. Add the remaining sugar and mash with a wooden spoon until smooth. Transfer the prune butter to a small bowl; set aside. Stir the lemon juice into the poppy seed filling; divide the lemon zest between all 4 fillings, stirring to incorporate.

Assemble:

Heat oven to 350°. Line an 8" square baking pan with 2 overlapping sheets of parchment paper cut to 10" x 8". Divide the dough into thirds; set 1 third aside. Cut 2 dough pieces in half and set aside. Transfer the third dough piece to a floured work surface and roll to 1⁄8" thickness. Line the bottom and sides of the baking pan with dough and let the excess dough hang over the edges; trim dough to within 1" of pan and brush with butter. Transfer the poppy seed filling to the bottom layer of dough and smooth the top with a spatula. Roll 1 piece of the remaining dough to 1⁄8" thickness and trim to make an 8″ square; top the poppy seed filling with dough and brush with butter. Transfer the apple mixture to the top of the dough and smooth with a spatula. Roll another piece of the remaining dough to 1⁄8" thickness and trim to make an 8" square; top the apple filling with dough and brush with butter. Transfer the walnut mixture to the top of the dough and smooth with a spatula. Roll another piece of the remaining dough to 1⁄8" thickness and trim to make an 8" square; transfer the dough to top of walnut filling and brush with remaining butter. Transfer the prune mixture to top of the dough and smooth with spatula; fold the overhanging dough onto the prune filling. Roll the remaining dough piece to 1⁄8" thickness and trim to make an 8" square; top the prune filling with dough, prick with a fork, and brush with the egg wash. Bake until the pastry is golden brown, 1 hour. Transfer to a rack and let cool 6 hours.

Using edges of parchment paper as handles, lift the pastry from pan and transfer to a cutting board. Cut flodni into 1 1⁄2" squares and serve.