Dark chocolate shortbread with white chocolate

ingredients:
75 g white chocolate
20 g milk
For the shortbread:
100 g flour
50 g butter
30g sugar
1 egg yolk
1 tablespoon water
1 tablespoon cocoa
method :
1. Prepare the ganache: Melt the white chocolate with milk. Mix well and let cool in the fridge.
2. For the shortbread: knead very soft butter, egg yolk and sugar. Add the flour and cocoa.
3. Knead until a smooth paste, add a tablespoon of water if necessary, if the dough is too dry.
4. Let stand ten minutes.
5. Spread out on 3 mm thick. Cut out biscuits with cookie cutter and place them on the baking sheet.
6. Scoop out the center of half of them.
7. Bake about 10 minutes at 180 ° C.
8. Let cool, then garnish the whole shortbread white chocolate ganache.
9. Cover with hollow shortbread and press gently.
http://www.odelices.com/recette/sables-au-chocolat-noir-coeur-chocolat-blanc-r1900/