In a large mixing bowl (or stand mixer bowl), combine the warm milk, yeast, and 1 teaspoon of granulated sugar. Stir gently and let sit for 5-10 minutes until foamy, indicating the yeast is active.

Add the remaining 1/4 cup minus 1 tsp granulated sugar, salt, melted butter, and egg to the yeast mixture. Mix well.

Gradually add 2.5 cups of the flour, mixing until a shaggy dough forms. If using a stand mixer, attach the dough hook and knead on low speed for 5-7 minutes, adding the remaining 1/2 cup flour as needed, until the dough is smooth and elastic. If kneading by hand, turn the dough out onto a lightly floured surface and knead for 8-10 minutes.

Lightly grease a clean bowl with oil. Place the dough in the bowl, turning once to coat. Cover with plastic wrap or a clean kitchen towel and let rise in a warm place for 1-1.5 hours, or until doubled in size.

While the dough is rising, prepare the blueberry filling. In a small saucepan, combine the blueberries, 1/2 cup granulated sugar, ground cinnamon, and cornstarch. Cook over medium heat, stirring frequently, until the mixture thickens and blueberries begin to burst, about 5-7 minutes. If using frozen blueberries, cook slightly longer until the liquid reduces and thickens. Remove from heat and let cool completely.

Once the dough has doubled, punch it down gently. Turn the dough out onto a lightly floured surface and roll it into a large rectangle, approximately 12x18 inches.

Spread the 1/4 cup softened butter evenly over the rolled-out dough, leaving a small border on one of the long edges.

Evenly spread the cooled blueberry cinnamon filling over the butter layer.

Starting from one of the long edges, tightly roll the dough into a log. Pinch the seam gently to seal.

Using a sharp knife or unflavored dental floss, cut the log into 12 equal slices (about 1.5 inches thick).

Lightly grease a 9x13 inch baking dish. Arrange the sliced rolls in the prepared dish, leaving a little space between each.

Cover the baking dish loosely with plastic wrap or a kitchen towel and let the rolls rise in a warm place for another 30-45 minutes, or until puffy and almost doubled.

Preheat your oven to 375°F (190°C).

Bake the rolls for 25-30 minutes, or until golden brown and the internal temperature reaches 200-205°F (93-96°C). If the tops are browning too quickly, you can loosely tent with foil.

Remove from the oven and let cool slightly while you prepare the glaze.

In a medium bowl, beat the softened cream cheese and softened butter with an electric mixer until smooth and creamy.

Gradually add the powdered sugar, mixing on low speed until combined, then increase speed to medium and beat until light and fluffy.

Stir in the vanilla extract and 1 tablespoon of milk or heavy cream. Add more milk, 1 teaspoon at a time, until the glaze reaches your desired consistency (thick but pourable).

Pour or spread the glaze generously over the warm (but not hot) blueberry cinnamon rolls. Serve immediately.