Ready a bowl, add strong bread flour, fast yeast, salt, cocoa powder, sugar then use your hand or bread cutter to mix it well, this is the dry ingredients. Ready another bowl, add the warm milk, beaten egg and mix it well then add into the dry ingredients and mix it well until the bottom of the bowl doesn't leave any dry flour.
Once the dough has gathered together, turn it out onto the work surface and start to knead it for 10 to 15 minutes or until the gluten has formed. You can cut a small piece of dough and spread it very thin if you can see your finger though the dough, it means it is ready to add the butter, if not knead it longer. Please note the dough will not be smooth now. (Please see How to knead wet dough) Spread the dough and add the butter in, cover it with the dough then start to knead it again. It will become sticky and spread on the work surface. Use the bread cutter to gather the dough and continue to knead it for around 10 to 15 minutes or until it becomes smooth.
Or once it is gathered together, you also can slap it on the work surface, stretch the dough out and then fold it, then turn 90° and repeat same process until the surface becomes smooth.
Once the dough becomes smooth, cut a small piece of the dough and spread it very thin, if you can see your finger though the dough, and it does not break easily, this means the gluten is ready. Next roll it into a ball and put it into a bowl and cover with wrap or wet towel to prevent to dough from drying out. Put it in a warm place to do the first rest for 30 to 90 minutes or until it doubles in size.
Finger test to check if the dough has rested enough(See Notes 2). If the dough has rested enough, turn it out onto the work surface(if the dough is sticky, dust the flour on the surface). Use your fingers gentle push the air out and divide into 6 equal pieces. Next shape each piece into a small ball, use the outside edge of your hand to roll the dough in the other hand. This should stretch the top and give it a smooth look. Then at the bottom you want to pinch the dough together to seal the ball.
Then leave them on the work surface and allow to rest for 15 minutes, cover with wrap or wet towel.
Roll the dough into rectangles around 10cm*18cm, add the dark chocolate, the crystallised ginger and cut mixed peel, the roll it and seal it. Use both hands to roll in to a sausage with pointy ends.
Take the sausage shaped dough and place it top side down. The seal should be facing up. Next using either your hands or a rolling pin, flatten out the middle until it's about 5cm wide. Fold the dough in half, take the top point and meet the bottom point. Leaving about 1cm from the point, cut the dough up the middle. Then turn both sides, so the bottom turns in and the top turns out. This will create the heart shape. Cover the hearts with wrap or a wet towel and let them rest for 30 to 60 minutes or 1.5 or 2x as big.Preheat the oven to 200C, approximately 15 minutes before you are ready to bake. Once dough has proved put it into the oven and turn the oven temperature down to 180C and bake for 13 to 15 minutes. ( Depending on your oven you may need adjust the time or temperature). Once it has baked let it cool down completely, then enjoy!