In the bowl of a stand mixer fitted with the dough hook (or a large mixing bowl if kneading by hand), combine the flour, eggs, sugar, milk, and yeast. Knead on low speed just until the dough begins to come together. Gradually add the cold butter cubes, allowing each addition to fully incorporate before adding more. Once all the butter has been added, mix in the salt and continue kneading until the dough is smooth and elastic, about 12 to 15 minutes.

Transfer the dough to a lightly greased bowl. Cover with plastic wrap or a clean kitchen towel, and let rise at room temperature until it increases in volume by at least one-third. For best texture and flavor, refrigerate overnight.

Before shaping, divide the dough in half. Use one half for this recipe and reserve the other half for another pastry.

To make the almond cream, combine the almonds (or almond flour), softened butter, powdered sugar, egg, vanilla, cornstarch, and salt in a food processor or high-speed blender. Blend until completely smooth and creamy. Set aside.

To prepare the toffee glaze, place the heavy cream, cold butter, brown sugar, honey, and salt in a medium saucepan. Cook over medium heat, stirring often, until the mixture is smooth and slightly thickened, about 5 to 7 minutes. Remove from heat and stir in the sliced almonds. Add flaky salt, if desired.

Roll out the dough on a lightly floured surface into a large rectangle, about ¼ inch (6 mm) thick. Spread a generous, even layer of almond cream over the dough. Using a sharp knife or pizza cutter, slice the dough into long, even strips, then roll each strip into a spiral.

Line a 9-by-13-inch (23-by-33 cm) metal or ceramic baking dish with parchment paper. Pour the toffee-almond mixture into the bottom of the dish and spread it out evenly. Arrange the rolled buns on top, leaving space between them to rise.

Cover the pan loosely with plastic wrap or a towel and let rise at room temperature for 40 to 50 minutes, or until the buns have increased in size by about 50%.

Preheat the oven to 330°F (165°C), preferably with convection.

Bake for 25 to 30 minutes, until golden brown and fully baked through. Let the buns cool in the pan for 10 minutes, then carefully invert the dish onto a large platter or tray so the toffee topping becomes the top.