Preheat oven to 375 degrees F (190 degrees C). Mix canned ham, dried onion, 1 teaspoon of poppy seeds, and margarine together in a bowl until thoroughly combined. Separate the biscuits; press 5 biscuits onto an ungreased baking sheet so each biscuit is flattened and about 3 1/2 inches in diameter. Spoon about 2 tablespoons of ham mixture into the center each flattened biscuit. Fold Swiss cheese slices to break into quarters and place 4 quarters atop the ham. Spoon the remaining ham mixture over the Swiss cheese pieces. On a floured work surface, lightly press remaining 5 biscuits into 4-inch circles. Lay a 4-inch biscuit circle onto of each topped biscuit and lightly stretch the top biscuit to cover the filling. Press the edges together lightly but do not seal tightly together. Sprinkle each filled biscuit with a pinch of poppy seeds for garnish. Bake in the preheated oven until biscuit tops are golden brown and the filling is hot, 10 to 15 minutes. Serve warm.