Heat half of the water (2 cups) to a simmer. Add the salt and stir until it dissolves. Pour in the remaining 2 cups of water and refrigerate until fully chilled.
Add the duck hearts, making sure they’re submerged. Refrigerate for 1 hour. Drain, rinse quickly under cold water, and pat completely dry with paper towels.
Make the glaze.
While the ducks are brining, make the glaze. Add the orange juice, red wine, butter, dried cherries, ginger, garlic, and rosemary to a small saucepan. Bring to a slow simmer over medium-low heat.
Cook, stirring occasionally, until the liquid is reduced and lightly coats the back of a spoon, about 25 minutes. Strain into a bowl and whisk to emulsify.
Skewer and season the hearts.
Thread the duck hearts onto metal or soaked wooden skewers. Brush all sides lightly with olive oil. Season with kosher salt and black pepper (use a little less salt if you brined).
Preheat the grill.
Preheat a grill to medium-high heat. Clean and oil the grates to minimize sticking.
Grill the duck hearts.
Place the skewers on the grill. Cook for 2–3 minutes total, turning as needed for even browning. Cook until just cooked through.
Glaze and finish.
During the last minute of grilling, brush the hearts with the glaze. Remove the skewers from the grill. Use any unused glaze as a dipping sauce.
NOTES
Brining is optional but recommended: The 1-hour brine seasons the hearts and helps them stay juicy on the grill. If you skip it, season more assertively with salt before cooking.Doneness: Duck hearts are best cooked hot and fast. This will help prevent them from drying out.Skewer tips: If using wooden skewers, soak them in water for at least 20–30 minutes before grilling so they don’t burn.Alternative sauce: To save time, you can use my homemade duck sauce as a glaze and dipping condiment.