1. Preheat the oven to 180°C and make sure the butter is not taken straight out of the refrigerator, as it is much easier to blend when slightly soft.
2. Mix the soft butter and flour. Add a pinch of salt and the egg yolk. Don’t knead the dough as the butter will melt – just carefully fold until you get an even dough.
3. Put the dough in the refrigerator for 30 minutes.
4. Roll it into 4-6 small circles or 1 large one depending on the size of your cake tin.
5. In a pan melt 15 g butter and add spinach. Sauté until the edges of the leaves start to soften. Mix eggs, crème fraiche, salt and pepper with spinach and add to the cake tins.
6. Top with tomatoes cut in half and Castello® Creamy Blue. Bake for 20 minutes at 180°C until the top is slightly golden.