Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper.
Lay the brioche slices on the baking sheet. Spread 1 TBSP jam over each slice.
Make the almond cream (frangipane): In a bowl, cream together softened butter and sugar until light. Add almond flour, vanilla extract, almond extract (if using), egg, and milk. Mix until smooth.
Spread almond cream over the jam-covered bread slices, covering fully to the edges.
Sprinkle sliced almonds evenly on top. Bake for 14–16 minutes, until golden and puffed.
Dust the bostock with powdered sugar if desired.
Serve warm with fruit and milk.