Set the oven to 180°C / 360°F with the fan.
In a food processor with a steel blade, place the pistachios and begin to crush them into small pieces but not like a powder.
Add the flour, butter and sugar and continue processing until you get a crumbly mixture.
Transfer the crumbs to a baking pan and bake for 10 minutes.
Set the crumbs aside to cool.
In a bowl, place the white chocolate and whipping cream.
In 30 second rounds in the microwave, melt the chocolate with the cream. You can also do it on top of a pot with boiling water - it just may take longer.
The chocolate needs to melt completely and the batter needs to be smooth and unified.
Cool the chocolate and cream batter in the fridge for 1 hour.
In a stand mixer with the whipping attachment, whip the cooled chocolate cream batter to stiff peaks.
Place the mousse in a piping bag.
Prepare the cups you want to use to serve the dessert with.
Start building the layers - start with the pistachio crumble, pipe a layer of the white chocolate mousse and then add pomegranate seeds. Continue adding layers to fill the cups.
Keep the cups in the fridge until you serve the dessert.