Pre-heat oven to 350F. Generously butter a 10-inch shallow baking dish.
Arrange cut croissants into dish, in two layers.
In a large bowl, whisk together eggs, egg yolks, milk, cream, sugar, orange zest and sea salt.
Crush saffron in a pestle and mortar, till it resembles powder. Add saffron to the egg mixture, whisk well to combine.
Pour this egg mixture over the croissants, and press gently with a spatula, so that the croissants absorb all the liquid.
Place in the middle rack of the oven and bake for 40 minutes.
When cool, dust with confectioner’s sugar, pistachios and rose petals.