For the blueberries preparation:
- Set the blueberries in the mixer and pour its juice in a casserole with whisked eggs, sugar and a pinch of salt.
- Cook at low heat while continuously mix it all. When the preparation cool down, gradually add butter and continue to stir.
- Wait for the butter to be well incorporated and for the preparation to thicker to remove from the stove. Never boil the preparation.
- Cool down for a moments and pour the preparation over all the shortbread surfaces.
- Set in the oven for 25 to 30 minutes aproximatively. Cool down and refrigerate till it gets completly cold. Slice into squares then serve.