pre heat oven to 375°f
in a large bowl cream together brown sugar and melted butter until fully combined
to the bowl add egg and vanilla, then whisk together. set bowl aside.
in a separate bowl sift flour, baking soda, and salt. Then add the dry ingredients to your bowl of wet ingredients.
using a wooden spoon or spatula fold ingredients together until you don't see any of the dry ingredients and everything is well combined.
add blueberries and gently fold them in, being careful not to squish the berries too much but a little is ok.
cover and allow the dough to rest in the fridge while you make the crumble topping.
in a small clean bowl add flour, brown sugar, oats, cinnamon, baking powder and salt, stir to combine.
cube the cold butter into 1-inch cubes and drop it onto the dry ingredients in the bowl.
using a fork or your fingers pinch, and crumble the butter together until everything is incorporated. you should be able to form a ball when squeezed like a snowball.
line a large baking sheet with parchment paper or a silicon mat and spoon 1.5 tbsp sized mounds of the cookie dough within 2 inches of space between each cookie
with your hands grab a pinch of the crumble topping and press it into the top of each cookie.
bake the cookies for 8-10 minutes until cookie is golden on the edges and the center is no longer shiny.
allow cooling on the tray for a few minutes before transferring them to a cooling rack to cool completely.
store in an airtight container and enjoy