Follow the directions for your bread machine, or place the warm water, half and half, eggs, sugar, blood orange agrumato olive oil, and yeast in bowl of standing heavy-duty mixer; stir until yeast dissolves. Fit mixer with dough hook. Add flour, zest, and salt to bowl and mix on low speed just until flour combined, about 10 seconds. Scrape down the sides of the bowl and increase the speed to medium and beat until dough comes together, about 3 minutes.
Cover bowl with plastic wrap. Let the dough rise at room temperature until almost doubled in volume, about 1 hour. Gently deflate the dough and cover bowl with plastic; chill dough overnight.
Line a baking sheet with parchment paper. Divide dough into 4 equal pieces. Make a short log from each piece and cut each log into 4 equal pieces. Roll each piece into a bun. Gently push a 1/2" piece of dark chocolate in the center of each bun and pinch the bottom of each bun to seal securely. Arrange the buns about an inch apart, pinched side down on the prepared sheet pan and allow to rise, covered, for 1 hour.
Preheat oven to 375°F. Gently brush top of the buns with the beaten egg glaze. Bake until buns are golden brown and fragrant, about 25 minutes.
Allow the buns to cool for 5 minutes. For Sweet Orange Glaze, mix together the orange juice, half and half, and confectioners' sugar. Brush each bun with glaze. Serve warm while the chocolate is still molten in the center.
Makes 16 buns