Preheat the oven to 170°C. Grease and line two 20cm cake tins.
Make the saffron milk. Place the butter and sugar in a bowl and beat until light and fluffy and almost white. Add the eggs a little at a time, making sure to keep mixing. Then add the flour, baking powder and saffron milk, and fold the mixture until you have a smooth, shiny batter.
Divide the mixture between the two tins and level the tops. Bake for 30–35 minutes.
Meanwhile, make the milk drizzle by mixing the milk powder with the boiling water in a bowl. Add the ground cardamom seeds and mix.
As soon as the cakes are out of the oven, drizzle the milk all over the top of both cakes and leave in the tin for at least 10 minutes before turning them out and removing them to cool on a rack.
To make the buttercream, put the crushed cardamom pods in a small bowl of the milk and leave to infuse.
Meanwhile, put the butter into a mixing bowl and whisk until very soft and light in colour. Add the icing sugar a little at a time, whisking after each addition, until all combined.
When the cardamom milk is ready, pour through a sieve into the buttercream and whisk until really light and fluffy.
Once the cakes are totally cool, place one cake on your serving dish and spread an even layer of buttercream over it.
Put the other cake on top, flipping it over so the milk drizzle top becomes the bottom and sandwiches the buttercream. Spread some buttercream evenly across the top and the sides and use a ruler to level off the edges.
If you have any cream left over you can pipe little kisses on top. Then gently take the rose petals and pistachios and press them into the bottom edge of the cake.
