01 - Line a large baking sheet with parchment paper and lightly grease your hands with butter or nonstick spray.
02 - Transfer popcorn into a large mixing bowl, discarding any unpopped kernels.
03 - In a medium saucepan over medium heat, melt the butter. Add corn syrup, granulated sugar, and salt, stirring continuously until the mixture reaches a gentle boil. Allow to boil for 2 to 3 minutes, ensuring sugar dissolves completely and the syrup becomes clear.
04 - Remove saucepan from heat and incorporate vanilla extract into the syrup.
05 - Quickly pour the hot syrup over the prepared popcorn and stir promptly with a wooden spoon or heatproof spatula, ensuring even coating throughout.
06 - Mix in candy corn and mini marshmallows, folding gently until just distributed.
07 - Once the mixture is cool yet pliable (approximately 2 to 3 minutes), use greased hands to shape into 3-inch balls, pressing gently to maintain structure.
08 - Place popcorn balls onto the prepared baking sheet and allow to cool fully before serving.