1. Crush cookies for the base by pulsing almond or oat cookies in a food processor or sealing them in a bag and rolling with a rolling pin until you have fine crumbs.

2. Mix cookie crumbs with toasted chopped almonds, granulated sugar, melted butter, and salt until the mixture resembles damp sand.

3. Press the mixture firmly into 8 tart rings or onto parchment lined plates using a round cutter as a guide to form even cookie bases. Chill the bases in the refrigerator while you prepare the mousse.

4. Bloom the first portion of powdered gelatin for the mousse by sprinkling it over the cold water in a small bowl and letting it sit for 5 to 10 minutes.

5. Melt the chopped bittersweet chocolate with the butter in a heatproof bowl set over a pan of simmering water or in short microwave bursts, stirring until smooth, then let it cool until warm but not hot.

6. In a mixing bowl, whisk softened mascarpone with powdered sugar, vanilla, and a pinch of salt until smooth and creamy with no lumps.

7. Stir the melted chocolate into the mascarpone mixture until fully combined and glossy.

8. Whip the cold heavy cream to soft peaks in a separate bowl, then gently fold the whipped cream into the chocolate mascarpone mixture in two or three additions to keep the mousse airy.

9. Gently warm the bloomed gelatin just until melted, then whisk in a spoonful of the mousse to temper before folding this mixture back into the full bowl of mousse until no streaks remain.

10. Transfer the mousse to a piping bag or use a spoon to fill silicone half sphere molds, tapping the mold lightly on the counter to remove air bubbles and smoothing the tops with an offset spatula.

11. Freeze the filled molds for at least 4 hours or until the domes are very firm, preferably overnight for easiest glazing.

12. For the mirror glaze, bloom the second portion of powdered gelatin in cold water in a small bowl and set aside.

13. In a saucepan, whisk together water, granulated sugar, heavy cream, and sifted cocoa powder, then bring the mixture to a gentle boil over medium heat while whisking until the sugar dissolves and the cocoa is smooth.

14. Remove the pan from the heat, add the bloomed gelatin, and whisk until completely melted and incorporated, then strain the glaze through a fine mesh sieve into a jug to remove any lumps or bubbles.

15. Let the glaze cool, stirring occasionally, until it is thickened slightly but still pourable and cool to the touch, which helps it coat the frozen domes smoothly and stay shiny.

16. Place a wire rack over a rimmed baking sheet and carefully unmold the frozen domes onto the rack, flat side down, spacing them apart so the glaze can run off.

17. Starting at the top center of each dome, pour the mirror glaze in a steady circular motion, letting it flow down and fully cover the sides; avoid touching the glaze once poured so it can settle into a smooth glossy layer.

18. Allow excess glaze to drip off for several minutes, then use an offset spatula to lift each dome and set it onto a chilled cookie base.

19. For the mascarpone swirl topping, whisk cold mascarpone with powdered sugar and vanilla until smooth, then whip the cold heavy cream to soft peaks and fold it into the mascarpone until thick and pipeable.

20. Transfer the mascarpone cream to a piping bag fitted with a star or round tip and pipe a tall swirl onto the top of each glazed dome.

21. Garnish each dessert with a small chocolate cookie or chocolate shard pressed gently into the mascarpone swirl and drizzle with a little extra melted chocolate or leftover glaze if desired.

22. Chill the assembled domes in the refrigerator for at least 20 to 30 minutes before serving so the centers soften from frozen to a silky mousse texture while the shape remains neat and defined.