Make the Brioche Dough

1. Heat half the sugar with the milk until lukewarm, then remove from heat and sprinkle yeast on top. Let it sit for 10 minutes until foamy.
2. In a stand mixer with a kneading hook, mix the yeast mixture with the egg. Add flour, remaining sugar, and salt. Knead for 3 minutes.
3. Slowly add butter, one piece at a time, and continue kneading for 10 minutes until dough is elastic and shiny.
4. Cover dough with plastic wrap and let it rise at room temperature for 1-2 hours until doubled.
5. Punch down dough, reshape into a ball, and refrigerate for at least 8 hours (up to 24 hours).

Bake the Brioche

6. Grease a 9-inch (23 cm) springform pan. Roll out dough to fit the pan and place inside.
7. Cover and proof for 1-2 hours until doubled.
8. Prepare almond topping: In a saucepan, cook sugar, honey, salt, and butter for 3-4 minutes. Remove from heat, stir in almonds, and cool.
9. Preheat oven to 180°C (356°F).
10. Spread the almond topping evenly over the dough. Bake for 45 minutes, covering with foil after 25 minutes if browning too much.
11. Let cool for 3 minutes, then remove the springform ring. Cool completely.

Make the Pastry Cream

12. In a bowl, whisk sugar and egg yolks until fluffy, then mix in cornstarch, flour, and vanilla.
13. In a saucepan, bring milk to a simmer, then slowly whisk into egg mixture.
14. Return mixture to heat and cook, whisking, until thickened (about 1 minute after boiling).
15. Remove from heat, stir in butter, and mix until smooth. Cover with plastic wrap and chill completely.

Assemble the Cake

16. Slice the cooled brioche horizontally with a serrated knife.
17. Pipe or spread pastry cream onto the bottom half.
18. Place the top layer back and dust with powdered sugar before serving.