1. Prepare the dough for the crust by mixing the water with the apple cider vinegar. Place it in the fridge for some time (or add an ice cube) to cool it down. Mix the flour with sugar and salt in a large bowl, add the cold butter in small pieces, and cut with a knife or pastry blender into pea-size pieces. Gradually add the cold vinegar-water mix and knead quickly with your hands until the dough starts coming together. The dough should not be wet or sticky. Wrap in plastic wrap and place in the fridge for about 45-60 minutes.

2. Roll out the dough on a floured surface slightly larger than a 9 inches (23cm) pie dish. Transfer and press to the bottom and sides, tuck in the edges and create a nice edge – use your fingers or a fork to create a pattern. Make sure the dough edge is slightly higher than the pie dish. Prick the bottom several times with a fork and place it in the fridge for another 10-15 minutes.

3. Preheat the oven to 325°F (160°C). Chop the walnuts and chocolate and place both inside the prepared pie crust. Add both sugars, flour, and salt to a large bowl. Melt the butter, add to the bowl and mix in. Make sure the mix is only slightly warm when adding the eggs and vanilla or the eggs will curdle – mix everything until well combined. Pour over the walnuts and chocolate pieces and bake for about 55-60 minutes in the preheated oven – the filling should have set completely. Take out of the oven and let cool down completely on a wire rack – for at least 2-3 hours. Serve with some whipped cream or ice cream.