Preheat oven to 350 degrees F. Line an 8-by-8-inch square baking pan with parchment paper or aluminum foil and lightly coat with butter.
Combine flour, brown sugar, cocoa, salt, and baking powder in a large mixing bowl or the bowl of a stand mixer.
Cut butter into chunks and add to bowl with flour; mix on medium-low speed until butter breaks up into pea-sized chunks. Mix in extracts. Add oats and mix until dough comes together in crumbles.
Press about ⅔ of the crumb mixture (~325 grams worth) into prepared baking pan. Spread jam in an even layer on top. Finally, crumble remaining dough evenly over top. Sprinkle with chopped chocolate and flake salt to finish (optional).
Bake for 30 to 35 minutes or until jam is bubbly around the edges. Place on a wire rack to cool completely before slicing into bars and serving.
