Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan or line it with parchment paper.
In a medium bowl, whisk together the flour, butterscotch pudding mix, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream the softened butter and sugar until light and fluffy using an electric mixer, about 2-3 minutes.
Beat in the eggs one at a time, followed by the vanilla extract, until well combined.
Add the dry ingredient mixture in batches, alternating with the milk and sour cream. Mix until just combined, being careful not to overmix.
Pour the batter into the prepared loaf pan, spreading it evenly with a spatula. Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
For a sweet glaze, whisk together powdered sugar, milk, and vanilla, then drizzle it over the cooled bread.