Place warm water in a large mixing bowl. Sprinkle yeast over the top and let sit for 5 minutes for the yeast to activate. Set aside a parchment-lined baking sheet.
Add the eggs, melted butter, 7 cups of flour, sugar, and salt to the yeast mixture and mix until dough is smooth and elastic, about 10 minutes by hand, adding more flour if needed.
Place dough in a lightly oiled bowl, cover, and let sit in a warm place to rise until doubled in size, about 45 – 60 minutes. While dough proofs, make the almond filling.
To make the almond filling, cream butter and sugar until light and fluffy. Add egg whites and almond extract and mix until combined, then add almond flour and mix until a smooth paste forms. Set aside until ready to use.
Once the dough has doubled in size, place it on a well-floured surface. Divide into two equal parts. Keep one half covered while you roll out the other half to a 9x13-inch rectangle.
Cut the rectangle into three 3x13-inch strips. Spread each strip generously with the almond filling, leaving a small strip empty along the long edge of each piece. Gently roll-up each strip into a cylinder, sealing at the unfilled edge. Arrange the three cylinders next to each other and braid into a long loaf. Tuck each end into the middle under the loaf and set on the prepared baking sheet. Repeat this process with the remaining half of dough.
Cover the loaves and let rise in a warm place until doubled in size, about 30 – 45 minutes. Preheat oven to 350°F.
Gently brush each loaf with eggwash and top with sliced almonds and sparkling sugar. Bake until deep golden-brown and an interior temperature reads 190°- 210°F 45 – 60 minutes.