Mix the cornstarch and water together in a very small bowl. Set aside. Combine blueberries and granulated sugar together in a small saucepan over medium-low heat. Stir constantly, bursting the blueberries against the sides of the pan. Once the blueberries have released some liquid, add the cornstarch/water. Turn the heat up to medium. Stir and cook for 3 minutes. Remove from heat and allow to cool completely. Mixture will thicken as it cools. I place it in the refrigerator to cool down quicker.

Optional: Before or after cooling, strain through a fine-mesh strainer if you don’t want blueberry chunks in your ice cream.

I find a fork works best for mixing the crumble. Mix the oat flour, brown sugar, and cinnamon together. Add the melted butter and mix until crumbles form. Set aside.

In a large bowl using a hand mixer or stand mixer fitted with a whisk attachment, beat the heavy cream on medium-high speed until stiff peaks form, about 4 minutes. Add the sweetened condensed milk and vanilla extract, then beat on low speed until just combined. Using a large spoon or rubber spatula, fold in the crumbles. Lastly, gently fold in 1/4 cup – 1/3 cup of the blueberry sauce, creating swirls. (Use any leftovers to spoon on top!)

Spoon/pour the ice cream mixture into a deep freezer-safe container or bowl. I suggest a 9×5-inch loaf pan. Cover tightly and freeze for at least 6 hours and up to 2 weeks.

Scoop, serve, and enjoy!