Mix the mixed berries with maple syrup and vanilla in a saucepan over the stove. Cook on low for ten minutes or until you reach a jam-like consistency. Mash the bigger pieces that remain. Optional: Stir in one tablespoon of cornstarch. This will make a creamier consistency when the popsicles freeze, but is not necessary.
Remove the saucepan from heat and whisk in heavy cream.
Place the remaining berries int the popsicle molds.
Pour the berries with cream into the molds.
Freeze the popsicles for at least 4 hours or until completely hard.