Prepare the pancake mix according to the package instructions, and measure 1 cup into a mixing bowl. Add the milk and heavy cream and use a small whisk to mix well. Chill for 1 hour. Churn in your ice cream maker for 30 minutes, adding the frozen blackberries for the last 1 minute. Pour into a square baking tray lined with parchment. Freeze for 2 hours. Put the remaining pancake mixture into the fridge.
Once the ice cream has set, cook the remaining pancake batter. Use a cookie cutter just smaller than the pancakes to cut out circles of ice cream, then sandwich between two pancakes. Serve immediately, with extra maple syrup and fresh blackberries.