Berry Swirl Ice Cream Sandwiches

Difficulty
Intermediate

For the Oatmeal Cookie Layers:

For the Berry Swirl:

2 cups Stalhbush Island Farms’ Marion blackberries (or any other Stahlbush berry or berry blend!)
4 tbsp granulated sugar
1 tbsp lemon juice
1 tbsp cornstarch
2-3 pints of dairy-free vanilla ice cream, softened to spread (but not melted)

For the Oatmeal Cookie Layers:

Preheat the oven to 350°F. Lightly grease and line a half sheet (18 x 13-inch baking sheet with ~1-inch sides) with parchment paper – allow some overhang on two opposing long sides for handles.
In a medium-sized bowl, whisk together the oats, flour, baking powder, cinnamon, cornstarch, and salt.
In a large bowl (or stand mixer with paddle attachment), beat the sugar, melted butter, milk, and vanilla extract together until blended/emulsified. Add the dry ingredients to the wet ingredients, mixing well to combine.
Pour the batter into the prepared baking sheet, spreading it out evenly. Bake on the middle rack of the preheated oven for 10 minutes, or until the sides of the cookies are just starting to darken but the center still looks soft. Set the hot baking tray on a cooling rack until room temperature. Slice in half so you have two cookie bars, each measuring 9 x 13 inches. Cover the tray with foil or plastic wrap, and chill in the refrigerator or freeze until ready to use. Chilling/freezing makes it easier to move without breaking during assembly.

For the Berry Swirl:

Add the blackberries and sugar to a small pot over medium heat. Stir the mixture until it starts to boil. Reduce the heat to low and allow the filling to simmer for 5-8 minutes. You want the berries to release their juices and concentrate a bit, but you don’t want them all to evaporate.
In a small cup, whisk the cornstarch and lemon juice together to make a slurry. Stir until the cornstarch is completely dissolved – any starch that is not dissolved will make lumps in your berries.
Over medium heat, whisk the cornstarch slurry into the hot berries. Whisk constantly to prevent burning and lumps from forming. Once the berry mixture is simmering, reduce the heat to low and cook one more minute so the cornstarch is fully activated. Remove from heat and pour the berry mixture into a bowl. Place a sheet of plastic wrap directly onto the hot fruit filling to prevent skin from forming. Refrigerate until completely chilled, about 2 hours or for up to 5 days if making ahead.

To Assemble the Ice Cream Sandwiches:

Line a 13 x 9-inch cake pan with parchment paper, leaving an overhang on the long edges. Place one half of the chilled cookie slab into the pan. Don’t worry if the edges of the cookies aren’t perfect, you can trim them later once fully assembled.
Loosely spread half of the softened ice cream over the cookie base – this does not need to be even or perfect looking, in fact, it’s better if it isn’t! Using a spoon, drop half of the chilled berry mixture over the first ice cream layer. Swirl the berries with the tip of a knife, or your spoon. Spread the remaining softened ice cream into the pan, and then the remaining berry mixture, swirling again. Do not overmix, or you’ll be left with purple ice cream without swirls. Level the top with an offside spatula, or the back of a large spoon. Top with the second oatmeal cookie slab, and press down very gently and evenly to eliminate air gaps. Quickly cover with plastic wrap or foil and freeze until set. This will take 3-8 hours depending on how cold your freezer is and how soft the ice cream was as you worked with it.
Using the parchment paper handles, lift the ice cream bars out of the pan and place them on a cutting board. Peel the parchment down from the sides of the ice cream sandwich. Using a large, sharp knife, cut into 16 rectangles, and enjoy! Leftovers should be wrapped in plastic or parchment, placed in an airtight container, and kept frozen for up to a few months.