CLEAN AND MARINATE THE VENISON HEARTS: Butterfly the hearts so that they lay flat on your cutting board. Carefully remove any sinew or tendons. Lightly season the hearts with kosher salt and let them rest at room temperature for 30 minutes. In a bowl, combine all of the ingredients for the heart (except the heart). Stir thoroughly to combine. Add the hearts and toss until they are fully coated. Cover and set aside while you make the beans and light the grill over high heat.
MAKE THE BEANS. In a pot over medium low heat, add the bacon and cook until the fat has rendered and the bacon is crispy. Remove the bacon from the pot and set aside while reserving about 1 tablespoon of the bacon fat in the pot. Add the garlic and onion. Cook while stirring often until the onions start to soften, about 4 minutes. Add the beans, stock and milk. Turn the heat to medium high and bring to a slow simmer, adjust the heat as needed. Cook the beans for about 20 minutes or until tender. Drain the beans while reserving the cooking liquid. Add the butter beans, onion, garlic and butter to a blender or food processor. Add about 1 cup of the cooking liquid. Start pureeing the beans, and with the motor running, add more cooking liquid as needed to achieve a smooth texture. Season with salt and pepper to taste. Cover to keep warm while you grill the hearts.
MIX THE GLAZE AND GRILL THE HEARTS: In a small bowl add the ingredients for the glaze and stir until combined. Over high heat, grill the hearts for about 2 minutes on one side. Glaze the heart and turn over. Glaze the cooked side while the other side is cooking. Cook for about 2 minutes.Pull the hearts from the grill and slather with a little more glaze. You don't want to cook them more than medium, or they will be rubbery and tough to chew. If you have an instant read thermometer, I like to pull mine at about 135 degrees F.
PLATE IT UP. Assemble each plate with a base of the butter bean puree. Slice the heat in about 1/4 inch sliced and lay on top of the puree. Crumble some of the bacon over top. If you like pepper, crack some fresh black pepper over top.
NOTES
Season the hearts before marinating. Butterfly them open, trim away the sinew and tendons, salt them lightly, and let them sit for 30 minutes before placing them in the marinade.
Do not marinate too long. A short marinade while you make the beans is enough, but you can hold them in the refrigerator for up to 6 hours if needed. Let them sit out 30 minutes to 1 hour before grilling.
Cook the beans until tender. Simmer the butter beans in the milk and stock until soft, then blend with the onion, garlic, butter, and enough cooking liquid to make a smooth puree.
Keep the grill very hot. Grill the hearts over high heat for about 2 minutes on the first side, glaze, flip, glaze again, and cook about 2 minutes more.
Do not cook past medium. Pull the hearts around 135 F if you are using a thermometer. Any farther and they start turning tough and rubbery.
Slice across the grain. Let them come off the grill, add a little more glaze, then slice about 1/4 inch thick before serving over the puree.
Make the puree ahead. The butter bean puree can be made up to 1 day ahead and reheated gently before serving.