Start by washing, peeling, and cutting your apples of choice into ½” pieces, and wash the raspberries, picking out any leaves/twigs.
In a medium saucepan, combine apples, raspberries, brown sugar, and butter over medium-low heat.
Stir frequently until butter is melted and sugar is dissolved, then add cinnamon, vanilla extract, salt, and cornstarch. To better incorporate the cornstarch, mix desired amount into the cold water and dissolve with a spoon fully before adding to the apple mixture.
Increase heat to medium and bring to a rolling simmer. Simmer for 5 minutes, stirring occasionally so raspberries don’t burn.
Use a potato masher or big fork to mush apples and raspberries into a smaller, more jam-like consistency. The apples may not smush as well, but that’s alright for this recipe.
You may need to cook this a little longer or add more cornstarch if the compote isn't thickening to that jammy consistency. If using the cornstarch method, increase by 1 tsp. increments, combining with a little cold water to dissolve before adding. A little cornstarch goes a long way!
Remove from heat and allow mixture to cool at least 15-20 mins. before including in the cookies.