Clean the chicken hearts by removing the skin and the ends of the veins. Finely chop the large onion and bell peppers. Cut the bacon into small pieces.
Heat some clarified butter in a large pan over medium-high heat. Add the bacon and fry for 2-3 minutes until starting to brown. Add the cleaned chicken hearts and cook for 4-5 minutes, stirring occasionally, until lightly browned.
Add the chopped onion and bell peppers and fry over medium heat for 3-4 minutes until softened.
Deglaze the pan with the red wine (roughly 1 shot), scraping up any browned bits. Let the wine reduce for 2 minutes over medium heat.
Pour in the chicken broth (0.5 liter), add the paprika powder and marjoram. Bring to a simmer over medium heat and cook for 20 minutes until the chicken hearts are tender and reach an internal temperature of 74°C (165°F).
Season to taste with salt and pepper. If desired, continue cooking uncovered for 2-3 minutes over medium heat to further reduce and thicken the sauce.
Serve hot with mashed potatoes, baguette, pasta, or rice.