Before anything put your chocolate chips in the freezer.
In a stand mixer fitted with the dough hook, add the flour and sugar. Mix until combined.
Add the milk, egg, egg yolk, yeast, orange zest and honey. Mix on low speed until the dough is well combined.
With the mixer still running on low speed add the butter one cube at a time. Continue to mix until the dough is smooth and does not stick to the sides of the bowl.
Mix in the chocolate chips.
Transfer the dough to a clean bowl and cover it with plastic wrap. Let it rise at room temperature until it doubles in size (2-3 hours).
Divide the dough into pieces that weigh about 60g each. Shape each piece into a bun, keeping the bun in between your palm and the work surface to create tension on the outside of the bun. This guy gives a good explanation here:
Put the buns on a parchment lined baking sheet keeping a good distance between them. Cover them with a clean dish towel and let them rise again for 1-1½ hours.
Whisk together 1 egg and a tbsp of milk. Brush each bun with the wash and bake at 350°F for about 15 minutes or until nicely golden on top.
They stay good for a couple days in an air tight container. You can also freeze them individually and let them thaw at room temperature when you want one!