Start by preparing the pound cake batter. In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. In a large mixing bowl, cream the unsalted butter and granulated sugar together for about 3-5 minutes until light and fluffy. Beat in the large eggs one at a time, followed by the vanilla extract. Gradually alternate adding the dry ingredients and whole milk, mixing just until combined.

Preheat your oven to 350°F (175°C) and grease a Twinkie pan with butter or non-stick spray. Pour the pound cake batter into the prepared pan, filling each cavity about three-quarters full. Bake for 18-22 minutes, or until evenly browned and a toothpick comes out clean. Let cool in the pan for a few minutes before transferring to a wire rack.

While the pound cakes cool, prepare the peach filling. In a medium saucepan, combine the diced peaches, a splash of lemon juice, and sugar. Simmer for about 8-10 minutes. Sprinkle in the cornstarch while stirring to thicken. Cook until syrupy and let cool to room temperature.

Once the cakes are cool, hollow out a section from each cake for the filling. Spoon the cooled peach mixture into each hollowed cake generously.

Prepare the glaze by whisking together the powdered sugar and heavy cream (or milk) until smooth. Drizzle over the filled Twinkies and serve immediately or chill briefly before serving.