For the Blueberry Jam

• Add the blueberries, sugar, lemon juice, and water to a small sauce pan over medium heat. Stir occasionally and add a pinch of salt. The blueberries will start to burst open and create a little sauce. Use your spoon to help squish them a bit. Bring to a slow boil.
• Stir the cornstarch with 2 tsp of water until smooth. Then, while the jam is still bubbling, stir in the cornstarch slurry until combined. Let continue to cook until the jam has thickened enough to coat the back of a wooden spoon.
• Set aside to cool. The jam will continue to thicken as it cools.

For the Blueberry Cookies

• Brown the butter by melting it completely in a saucepan, then continue to cook it until it reaches a golden brown color and smells nutty. At first it will start to pop and crack, then after 3-5 minutes it will quiet down and begin to foam up as it toasts.

• Transfer the browned butter into a wide glass bowl and allow to come to room temperature. You can do this in advance, or just pop it into the freezer and  stir every 5 minutes until it reaches a thick, spreadable consistency.

• Then, add the cooled browned butter and sugars to the bowl of a stand mixer with the paddle attachment. Cream the butter and sugars on medium speed for 3 minutes. It should become pale in color and have a very light and fluffy texture.

• Add the egg, egg yolk, and vanilla and mix for another 3 minutes, until the mixture thickens up and has a glossy sheen.

• In a separate mixing bowl, whisk together the flour, baking powder, salt, and cinnamon. Add the dry ingredients to the wet and mix until just combined with a few streaks of flour remaining.
• Fold the blueberries in gently with a rubber spatula being careful not to squish them. 

• Use a large 3 TBSP cookie scoop to portion the dough to portion the dough. Then, roll the dough into balls in the palms of your hands.

Then, take the back of a tablespoon to make a well on top of the cookies. Add 1 tsp of blueberry jam into the well of each cookie. Pop the cookie sheet into the fridge for at least 30 minutes, up to overnight.

For the Streusel Topping

• When you are ready to bake the cookies, preheat the oven to 350 and make the streusel.

• In a mixing bowl, whisk together the brown sugar, cinnamon, and flour. Cut the cold butter into a small dice and then cut it into the flour/sugar mixture using a pasty cutter or a fork. Once it’s pretty well incorporated, use the tips of your fingers to continue squishing the butter in. You want the butter to be in pea sized pieces.

• Arrange the cookies onto two parchment lined cookie sheet and sprinkle about 1 TBSP of streusel onto the cookie dough. They won’t spread too much, but give them some space in between.

• Bake at 350 for 15 minutes. Then allow the cookies to sit on the hot cookie sheet for 2-3 minutes before transferring to a cooling rack to cool completely.