In a medium saucepan over medium heat, combine frozen blueberries, sugar, lemon juice, lemon zest, and a pinch of salt. Let simmer for 5–7 minutes until jammy. Remove from heat and cool completely.

In a large mixing bowl, whisk together egg, sourdough discard, warmed milk, vanilla extract, lemon zest, and granulated sugar. In another bowl, mix flour, baking powder, baking soda, and salt. Combine wet and dry ingredients until shaggy dough forms.

Transfer dough to a floured surface and knead in softened butter until smooth and elastic, about 3–4 minutes. Cover with a towel while preparing next steps.

Preheat oven to 350°F (175°C) and grease a baking pan. Roll dough into a rectangle ½ inch thick. Spread butter over the dough, then evenly add cooled blueberry compote. Roll tightly and cut into 9–12 pieces.

Bake rolls for about 30 minutes, or until golden brown. Allow to cool slightly in the pan before glazing.

In a mixing bowl, beat cream cheese and butter until fluffy. Mix in vanilla, lemon zest, lemon juice, and powdered sugar until smooth. Adjust consistency with milk if needed.

Drizzle glaze over warm rolls and serve immediately for the best flavor.