Preheat your oven to 350°F (175°C) and grease an 8-inch baking pan or line it with parchment paper.

In a medium saucepan, combine sugar, pumpkin purée, oil, and butter over medium heat, stirring frequently for about 3-5 minutes until melted and smooth.

Remove the saucepan from heat and let it cool for 10-15 minutes. Stir in the egg until fully combined.

In a separate bowl, whisk together the flour and baking powder. Gradually mix this into the wet ingredients until smooth.

Pour the batter into the prepared pan and bake for 32-36 minutes, checking with a toothpick to ensure doneness.

Let the bars cool for about 15 minutes in the pan, then transfer them to a wire rack to cool completely.

In a microwave-safe bowl, combine milk, espresso powder, and a pinch of salt. Heat until dissolved, then stir in confectioners' sugar until smooth.

Pour the glaze over the cooled bars and allow it to set before cutting into squares.