Preheat oven to 350°F and line a baking tray with parchment paper. Set aside.
Cream the butter, granulated sugar together until light and creamy. Should take about 2 minutes. Add in the egg, vanilla extract, and continue mixing until smooth.
1/2 cup butter, 3/4 cups white sugar, 1 egg, 1 tbsp vanilla
Add in the flour, baking soda, baking powder, and salt. Fold this in, the dough will be dry. This is ok!
1 2/3 cups all-purpose flour, 1/4 tsp baking soda, 3/4 tsp baking powder, 1/4 tsp salt
Add the milk and mix until combined. Do not over mix. The dough should be soft now and come together.
1 tbsp milk
Gently fold in the blueberries. Drop tablespoons of the jam in the bowl and swirl it in. You want ribbons of the jam in the dough, so only mix it a few times!
1 cup fresh blueberries, 3 tbsp blueberry jam
Make the streusel by adding all of the ingredients in your bowl and using a fork to mix it until it turns crumbly and comes together. You may also use your hands to mix it.
3 tbsp butter, 2 tbsp brown sugar, 1 tbsp white sugar, 1/3 cup flour, 1/4 tsp cinnamon
Scoop out the dough onto your prepared baking sheet. Top with a spoonful of the streusel topping. Press it into the dough.
Bake the cookies for 15-18 minutes. Mine took 18. The cookies will look soft and fluffy. Remove from the oven and then leave them on the tray for a few minutes. The warmth of the tray will allow them to continue to bake. Top with extra streusel topping if desired!
Cool the cookies! As they cool, they will firm up. Enjoy!