In a large bowl mix together the flour, castor sugar, cocoa powder and salt.
Add the cubed cold butter and work into the flour. You can either use a pastry cutter or work with your hands. If you're using your hands, you have to work fast so as not to melt the butter. Rub in all the butter in the flour until you have a coarse mixture with small pebbles of butter. This process can be also done in a food processor.
Slowly add the milk and knead to form a smooth dough.
Once the dough is ready, wrap into some cling film and store in the fridge for at least an hour or two.
For the filling
Mix the strawberries together with the sugar, vanilla and cornstarch. Set aside and let them rest for a few minutes.
Preheat the oven to 220°C or 430°F.* Line a baking tray with parchment paper. Set aside.
On a floured surface open the pie dough into a large circle of about 5mm thickness. From the circle cut the heart shapes with your cookie cutter. I have used a shape of about 8cm in width.
Fill the centre of the heart with the strawberry mixture. Make sure to leave space around the edges of the filling.
Place another piece of heart dough on top and seal around the edges. You can either leave them as such or else press them down further with a fork.
Place the pies on the lined baking tray and brush the top and sides of the pies with the egg wash.
Bake the pies for about 20 minutes.
Melt the chocolate in the microwave or on a double boiler. Set aside.
Once the pies are ready, let them cool slightly before drizzling some of the melted chocolate on top.
*You can also make these in an air fryer with the following settings: 200°C and bake for 15 minutes.