In the large bowl, place the yeast, 1 tablespoon sugar and water. Mix and let sit for 10 minutes, or until thick. Add the remaining sugar, flour, cocoa, salt, oil, coconut oil, vanilla and eggs. Use a dough hook in a stand mixer on low speed or a spoon to mix together. Scrape down the sides of the bowl a few times. Continue to mix with the hook, or knead by hand, for 2 minutes.
Cover bowl with plastic wrap and let rise for 2 hours. Prepare the filling about 5 minutes before the dough us ready.
To make the chocolate filling, place the chocolate into a microwave-safe bowl and heat for 1 minute and mix. Heat for another 45 seconds and mix again. Heat for another 30 seconds and mix and, if not melted, heat for another 15 seconds. You may also melt the chocolate over a double boiler. Add the sugar, cocoa and oil and mix well. Place the bowl into the freezer for 5 minutes to firm up a little. Whisk again.
Grease two 8-inch loaf pans with spray oil. Divide dough in half. Place a piece of parchment paper about 20 inches long on your counter and sprinkle with a little flour. Place the dough on top and sprinkle with a little more flour. Roll the dough into a 12 X 16-inch rectangle so that the long side is facing you.
Spread 1/2 of the chocolate filling, about 1/2 cup all the way to the edges. Sprinkle 1/2 of the chips over the chocolate filling and roll up the long way. Roll the parchment paper over the roll and roll up. Place into the freezer for 5 minutes while you roll the second piece of dough as you did the first. Place into the freezer.
Grease 2 loaf pans. Remove the first roll from the freezer and unwrap onto the parchment paper with the seam of the roll on the bottom. Use a large knife to slice the roll in half the long way. Turn each half so that the cut sides face up. Lay one over the other to form an “ X.” Twist the two strands around each other, keeping the cut side facing up. Tuck the ends under the loaf so that they slightly overlap each other in the center. Place into the prepared pan and press down slightly. Repeat for the second roll.
Let rise for 30 minutes. Preheat oven to 350°F. Brush the top with the egg yolk mixed with 2 teaspoons water.
Bake for 35 minutes, or until medium-browned and firm to the touch. Let cool for ten minutes and then run a knife around the edges. Remove from the pan onto a cooling rack and let cool for another 15 minutes. Enjoy warm or at room temperature. Stored covered at room temperature for up to 5 days and reheat if desired.