1. Prepare the vanilla cream by combining the milk, heavy cream, granulated sugar, and butter in a saucepan. Cook over medium heat, whisking constantly, until the mixture thickens.

2. In a small bowl, whisk together the egg yolks and cornstarch. Temper the egg yolks by slowly pouring the warm cream mixture into the egg yolks, whisking constantly.

3. Return the saucepan to the stovetop and cook for an additional 2-3 minutes, or until the mixture thickens. Remove from heat and stir in the vanilla powder or vanilla bean.

4. Strain the cream through a fine-mesh sieve into a clean bowl and let it cool to room temperature, about 20°C (68°F).

5. Cover the bowl with plastic wrap, pressing the wrap directly onto the surface of the cream to prevent a skin from forming.

6. Refrigerate until chilled. Cut out eight round bases from the meringue, each slightly smaller than the glass cups you'll be using.

7. Use the same glass to cut out the marzipan bases. To prepare the marzipan decorations, use a small amount of pink marzipan to shape into roses. You'll need about 8 roses in total. Cut out four "locks" from the green marzipan. These will be used to decorate the top of each cake.

8. In a separate bowl, whip the heavy cream until stiff peaks form. Add a pinch of vanilla powder, if desired, for extra flavor.

9. To assemble the cake, place the first meringue base in the bottom of a glass cup. Spoon a layer of vanilla cream over the meringue, followed by another meringue base. Continue layering the meringue and vanilla cream until you reach the top of the glass cup. Finish with a marzipan lock and a rose.

10. Dust the top of each cake with confectioners sugar, if desired, before serving.