In a large bowl, mix together the flour, cocoa powder, sugar, salt, yeast, and cinnamon (if using).
Add the warm water, honey, and olive oil. Stir with a spoon until a sticky dough forms. Adjust texture if needed with a little more water or flour.
Fold in half the chocolate chips or chunks. Mix gently to distribute.
Cover the bowl with a clean towel and let the dough rise in a warm place for 1 hour, or until doubled in size.
Preheat oven to 200°C (400°F). Grease a 30 cm skillet or cake pan with olive oil and warm it in the oven for 2 to 3 minutes.
Carefully transfer the dough to the hot pan. With oiled fingers, press it out to the edges and dimple the surface.
Brush the top with olive oil and sprinkle with the remaining chocolate chips. Add coarse sugar or chopped nuts if using.
Bake for 17 to 20 minutes, until the top looks set and the center springs back lightly.
Let rest in the pan for 10 minutes before slicing. Serve warm with honey, whipped cream, or vanilla ice cream.