In a medium saucepan, combine frozen blueberries, granulated sugar for the jam, and cornstarch. Cook over medium heat for 20-25 minutes, stirring regularly, until thickened.

In a large mixing bowl, warm the whole milk and stir in the yeast and granulated sugar. Let it bloom for 5-10 minutes until frothy.

Add flour, salt, eggs, vanilla extract, lemon zest, and softened butter. Mix until a shaggy dough forms, then knead for 8-10 minutes.

Place kneaded dough into a greased bowl, cover, and let rise in a warm spot for 1-1.5 hours until doubled.

In a mixing bowl, combine softened butter, brown sugar, granulated sugar, lemon zest, lemon juice, and salt until creamy.

Punch down risen dough, roll out to a 1/4-inch thick rectangle. Spread lemon filling and drizzle blueberry jam on top. Roll tightly into a log and cut into 12 pieces.

Place cut rolls in a greased casserole dish, pour heavy cream over them and let rise for another hour.

Preheat oven to 350°F (175°C) and bake rolls for 22-25 minutes until golden brown.

Make frosting by blending butter and cream cheese until fluffy, then sift in powdered sugar and mix in reserved blueberry jam.

Spread cream cheese frosting on warm rolls and serve.