First up, peach syrup! Combine peach nectar and cinnamon in a medium saucepan. Bring to a boil, then reduce to a simmer. Stir every once and a while and just let it bubble away! You want this to reduce considerably to make a concentrated syrup. I let mine simmer for about an hour. Set aside to cool!
Using a stand mixer or handheld with a whisk attachment, whip up that heavy cream until it creates heavy peaks.
While that's whipping combine your peach syrup with the can sweetened condensed milk. (I poured mine into a liquid measuring cup! I had about ⅔ cup syrup. I wouldn't add more than a cup of syrup--it will mess with the texture of the ice cream.)
Once your whipped cream is ready, carefully fold in the peach mixture. You don't have to be too gentle! You want to make sure you're not totally deflating the whipped cream.
Grab a 9x13 pan and pour in half of your deliciously peachy mixture. Pause. Admire. Then crumble in half of your crisp, adding half a cup of frozen blueberries if you'd like.
Top with the rest of your peach mixture and spread evenly. It's okay if things get a little mixed up! You are not at the Louvre, my dear.
Top with the rest of your crisp and a few more blueberries then into the freezer it goes! Freeze until solid, about 6 hours.
Scoop and serve!