Wash and clean a whole heart. Cut off the fat on the top and any grisel on top that you can feel. Place in a large bowl or non metal container. Fill with cold water that will cover the heart. Pour salt over and set in refrigerator for 2 days, changing the water and salt every day. I have set a plate on top to keep it submerged..I have tried a zip lock bag but be very careful.
After heart has soaked. Pour off the salted water. Rinse heart. Place in pot, large enough to cover with water & has a lid. Add water.
Add salt & pepper to your taste, onion flakes (or diced onion), and garlic powder..(or a clove of garlic)
Bring to a boil. Turn down down to simmer and put on lid. Simmer for 3 to 4 hours. The longer it simmers, the more tender it will be. Add water as needed to keep heart covered. Poke heart with fork to feel how tender it is.
Remove heart and let cool enough to handle. Take a knife and peel off the outer layer(looks kind of like a thin skin). You can also trim the inside cavity a much as possible. Your pet will love the scraps.
Cut heart into thin slices and trim interior holes as needed. Place in ziploc to keep it from drying out.
You can also use an elk, moose or beef heart. Of course, they take longer to cook.
To make sandwich, use your choice of bread & your own sides and layer 3 or more slices on top. Salt and pepper to taste.