Warm the milk and add the yeast to it. Let rest for 15 minutes.
In your mixer with the hook attachment, mix flour, sugar and salt. Add milk+yeast and beaten egg. Knead for about 7 minutes, until all liquid is absorbed. Then add the butter. Knead for a good 10 minutes. The dough should become smooth and elastic, it shouldn’t stick as much to the bowl either.
Cover and let rest for 2 hours at room temperature.
Dice your pineapple. Melt the butter in a saucepan, add the pineapple and sugar. Let caramelized a few minutes.
Crush the hazelnuts, add half to the pineapple and reserve the rest.
Deflate the dough and divide into 6. Shape each portions of dough, and form a ball with a smooth, taut surface. Slightly press them to form a disc, add about one good tbsp of filling in the center, and foold the outer sides over the filling. Press well together the wedges to seal and place them seam down on a baking pan lined with parchment paper. Cover and let rise again for about 1 hour in a warm place.
Preheat your oven to 350C. Beat one egg and brush the brioches with it. Mix the remaining hazelnuts with about 10g of sugar. Sprinkle on top of the brioche.
Bake for 25 minutes. You can add powdered sugar on your brioche if you want before serving.