Chocolate Hot Cross Buns

Heat the milk in a medium saucepan until steaming but not boiling, then stir in the butter until melted.
In a large mixing bowl, whisk together the flour, cocoa powder, sugar, salt, and yeast until evenly combined.
Pour the warm milk mixture and beaten egg into the dry ingredients, stirring until a rough shaggy dough forms.
Knead the dough in a stand mixer on low speed for 5 minutes until smooth and elastic, or knead by hand for about 10 minutes.
Fold in both types of chocolate chunks and mix on low speed for 2 minutes until mostly incorporated. If needed, press in remaining chunks by hand.
Lightly oil a large bowl and place the dough inside, covering with a damp towel or plastic wrap. Let rise in a warm place until doubled, about 1–1 ½ hours.
Line a 13" x 9" pan with parchment paper. Turn the dough onto a floured surface and divide into 12 equal portions (around 70g each).
Roll each portion into a smooth ball and place in the prepared pan, leaving space between. Cover and let rise for 45–60 minutes until puffed and touching.
Preheat the oven to 375ºF (190ºC).
In a small bowl, combine the flour and water to form a thick paste (toothpaste consistency). Transfer to a piping bag and pipe crosses onto each bun.
Bake the buns in the middle rack of the oven for 20 minutes until dark brown and springy to the touch.
Warm the honey for 10–15 seconds in the microwave, then brush over the tops of the warm buns for a shiny finish.