Grease an 8x8 inch square pan. Preheat oven to 375°F/190°C
Cream the butter, sugar and vanilla with an electric mixer until light and fluffy. Add the eggs one at a time and beat until incorporated.
In a medium bowl, whisk the flour, baking powder and salt in a bowl. Add to the creamed mixture and mix until just blended. Take one cup of batter and spread on the bottom of the tin. Then, gently fold in the berries with the rest of the of the batter. Scrape batter into the pan.
Make Streusel
Mix flour, sugar, cinnamon, nutmeg and salt in a bowl. Add butter and crumble with your fingers until it resembles a coarse sand. Scatter over the cake batter.
Bake until the top is golden brown and cake has completely set, around 40-50 minutes. Cool and then cut into squares.
Cream Cheese Glaze
Beat cream cheese with an electric mixer until smooth. On low, add the icing sugar until well combined. Pour in the milk and vanilla, beating until smooth. Drizzle over the cooled bars.