For the pralines: Mix together the sugar, almonds, food coloring and 1/3 cup water in a pan. Bring to a boil over medium heat; do not stir until the water starts boiling, then you can start swirling the pan gently. When the liquid starts to thicken, after about 5 minutes, stir continuously until you feel a caramel texture. Take the pan away from the heat and stir until the sugar crystallizes, 12 to 15 minutes. Place the almonds on parchment paper and let them cool.
For the brioche: Stir together the flour, sugar, yeast and salt in a medium bowl. Gradually add the warm milk, butter and lightly beaten eggs into the flour mixture; knead until the dough is smooth and pulls away from the sides of the bowl. Cover the bowl, and allow the dough to rise until it is doubled in size, about 2 hours. Deflate the dough by placing your fingers under it, lifting a section of the dough, and then letting it fall back into the bowl. Work your way around the circumference of the dough, lifting and releasing. Cover the bowl tightly in plastic wrap and refrigerate overnight, during which time the dough may continue to rise and may double in size again.
Turn out the dough onto a floured surface. The dough must be cool to the touch, so only take out the dough immediately before you get started. Flatten the dough slightly, and then add 1 1/2 handfuls of the pralines in the center. Fold and shape the dough around the pralines so they are completely surrounded by the dough and both sides are closed. Flip the dough over so the new "seam" side is down and roll gently with both hands to shape and smooth out the dough.
Place the dough on a greased baking pan and let sit at room temperature until it doubles in size, about 2 hours.
Preheat the oven to 275 degrees F.
Whisk together the remaining egg and sugar to make an egg wash. Cover the dough with the egg wash using a pastry brush and sprinkle with the rock sugar.
Bake for 25 minutes with the oven door closed, then for another 15 minutes with the door open. This will ensure the brioche is baked evenly and does not brown too much on the outside.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.