Leopard Milk Bread

Make the Dough
2 Stir cornstarch in cup of warm milk until dissolved.
3 In the bowl of a stand mixer, combine milk mixture, yeast, and 2 Tbsp of the sugar. Gently stir together and let sit for 8-10 minutes until frothy.
4 Add melted butter (cooled to room temp), the rest of the sugar, salt, vanilla and orange zest to yeast mixture.
5 Using the dough hook attachment mix on medium-low speed. Slowly spoon in flour until fully incorporated. Increase speed to medium for about 1 minute. 
7 The dough should be very slightly tacky, with a soft and smooth texture and cling to the entire bottom of the bowl. Let the dough rest for about 10 minutes to allow the flour to absorb the liquid. 
9 Turn the mixer back on to medium speed and beat for 6-8 minutes to knead the dough until smooth and shiny.
10 Windowpane Test: Tear off a small piece of dough and stretch out gently with your fingers. If the dough becomes transparent without breaking its ready. If not, beat for another 2-3 minutes and test again.
11 Transfer the dough onto a lightly floured surface. Weigh the dough and divide into two equal halves.
13 Plain Dough: Lightly dust one dough half with flour, place in a bowl, loosely cover  with wrap in plastic wrap. Set in a warm location to double in size, about 2 hours. This will be our natural colored.
14 Chocolate Dough: Take the second dough half and evenly divide it into two equal halves. We will use these two halves for the chocolate spots.
Make Chocolate Pastes
16 Use a separate bowl for each paste. Stir the cocoa powder and milk together with a small spatula.
18 You should have one dark chocolate paste and one light chocolate paste.
19 Place on half in the dark chocolate paste and the other half in the light chocolate paste. 
20 Work the chocolate into the dough with your hands. Transfer to a work surface and knead to incorporate all the chocolate into each dough until its homogenous in color. 
21 You should now have one dark chocolate ball of dough and one light chocolate ball of dough.
22 Transfer each chocolate dough ball into a bowl, loosely cover with plastic wrap and place in a warm location to double in size. About 2 hours.
Divide the Dough
57 After all three doughs have doubled in size, transfer them to a lightly floured work surface. 
27 Weigh the light colored dough and divide into 6 equal pieces.
28 Repeat with the dark and light chocolate dough balls.
29 You should now have 18 pieces of dough.
Make Logs
30 Start by rolling each of the light brown pieces into an 8-inch log.
31 Then using a rolling pin, roll each of the dark chocolate dough balls into 9-inch flat ovals.
32 Place one light chocolate log onto a flat dark chocolate oval. Using a pastry brush lightly coat the edges of the dark chocolate with milk.
34 Then fold the dark chocolate over the light chocolate as if you were wrapping a hot dog bun around a hot dog. The result should look like a chocolate cigar.
36 Next, take a natural dough ball and roll into a 9-inch oval with the rolling pin.
37 Repeat the process by placing the dark chocolate wrapped 'sausage' onto the white dough oval.
38 Paint the edges of the white dough with milk and then fold it over the dark chocolate, closing the seems.
39 The result should now look like a log with a light chocolate center, a wrapping of dark chocolate, and then a final wrapping of white dough.
40 Repeat this process with the remaining dough until you have 7 logs.
41 Now, roll each log lengthwise with your hands, until it becomes doubled in length. Like a long snake. Slice each log in half for a total of 12 logs.
Line Pan and Proof
46 Prepare a 9x5-inch loaf pan with a light coating of non-stick baking spray. 
47 Stack the dough logs into the pan, alternating ends with each log.
48 Cover with a light tea towel and place in a draft free warm location to puff and double in size. At least 1 hour.
Bake Loaf
49 Preheat oven to 375℉ (190℃).
59 Beat the milk and egg together in a small bowl to make an egg wash. Lightly brush a thin layer across the top of the dough.
50 Reduce oven temp to 350℉ (176℃) and place the pan on the middle oven rack.
51 Bake for 35-45 minutes until golden brown and when the inner temperature reaches 190℉ (88℃) on an instant read thermometer.
52 Place pan on a wire rack to completely cool. Invert pan to remove the loaf.