Preheat your oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan, or line with parchment paper leaving an overhang on the long sides for easy removal.

In a medium bowl, beat the softened cream cheese with 1/4 cup granulated sugar until smooth and creamy. Beat in the egg yolk and 1/2 tsp vanilla extract until well combined. Set aside.

In a small bowl, gently toss the blueberries (fresh or frozen) with 1 tbsp granulated sugar, 1 tsp lemon juice, and 1 tsp cornstarch (if using). The cornstarch helps prevent the blueberries from sinking and keeps the swirl intact. Set aside.

In a large mixing bowl, whisk together the flour, 1/2 cup granulated sugar, baking powder, and salt.

In a separate medium bowl, whisk together the large egg, 1/2 cup milk, vegetable oil (or melted butter), and 1 tsp vanilla extract.

Pour the wet ingredients into the dry ingredients. Mix with a rubber spatula until just combined. Be careful not to overmix; a few lumps are fine.

Pour about half of the loaf batter into the prepared loaf pan and spread evenly.

Spoon dollops of the cream cheese filling over the batter, leaving some space between dollops.

Evenly sprinkle about half of the blueberry mixture over the cream cheese.

Carefully spoon the remaining loaf batter over the filling and blueberries, spreading gently to cover. Top with the remaining blueberry mixture.

Using a knife or skewer, gently swirl through the layers a few times to create a marbled effect, being careful not to overmix.

Bake for 55-65 minutes, or until a wooden skewer inserted into the center of the loaf (avoiding large pockets of cream cheese) comes out with moist crumbs but no wet batter.

If the top begins to brown too quickly, loosely tent with aluminum foil.

Remove the loaf from the oven and let it cool in the pan for 15-20 minutes before carefully lifting it out onto a wire rack to cool completely.

In a small bowl, whisk together the powdered sugar, milk (starting with 2 tbsp and adding more if needed), and vanilla extract until smooth and drizzly.

Once the loaf is completely cool, drizzle the glaze over the top. Let the glaze set for a few minutes before slicing and serving.