In a bowl, mix the softened cream cheese, sugar, and vanilla until smooth. Add the egg white and stir gently until just combined, keeping the texture light. Set aside.

In another bowl, whisk together the flour, baking powder, baking soda, and salt to evenly distribute the leavening.

In a large bowl, beat the butter and sugar for 2–3 minutes until light and fluffy. The mixture should look pale and airy.

Add the whole egg, egg yolk, and vanilla extract, mixing until fully incorporated. Scrape down the sides to keep everything even.

Gradually add the dry ingredients, alternating with the sour cream. Begin and end with the dry mixture. Stir just until combined to keep the cake soft.

Pour the batter into the pan and smooth the surface. Sprinkle about ⅓ cup blueberries over the batter, spread the cream cheese layer on top, then add the remaining blueberries.

Mix sugar and flour in a bowl, then cut in the chilled butter until the mixture becomes crumbly with a coarse texture.

Sprinkle the streusel evenly over the cake. Bake for 40–45 minutes, until a toothpick inserted into the cake layer comes out clean. If the top browns too quickly, cover loosely with foil near the end.

Let the cake cool completely in the pan before removing. Refrigerate for at least 1 hour so the cream cheese layer sets properly before slicing.