Line a 9" square baking pan with parchment paper, ensuring that there are handles on the sides for easy lifting of the baked cookies.

Preheat the oven to 355°F (180°C).

In a large bowl or stand mixer, combine softened butter, oil, brown sugar, and granulated sugar. Beat together until thick and creamy, scraping down the sides of the bowl for an even mix.

Add in the egg, water, vanilla extract, and sea salt, mixing thoroughly until well combined.

Gradually add the flour, baking soda, baking powder, oats, and cinnamon. Mix gently, just until combined.

Fold in the raisins, making sure they are evenly distributed throughout the dough.

Transfer half of the cookie dough into the prepared baking pan, spreading it evenly.

Bake in the center of the preheated oven for 10 minutes, or until golden on the edges and puffed.

Upon removing the cookies from the oven, gently press down any raised corners or edges with a spatula. Let cool for a few minutes, then carefully lift the cookie with the parchment paper onto a wire rack to cool completely.

Repeat the baking process for the second half of the cookie dough.

Once the cookies are completely cool, in a large bowl or stand mixer, whip the chilled cream with a whisk attachment until you achieve stiff peaks.

Add the vanilla bean paste, salt, and the can of sweetened condensed milk into the whipped cream. Fold gently until just combined for a smooth mixture.

Peel the parchment from one square of cookie dough and place the parchment back into the baking pan. Carefully invert the first cooled cookie onto the parchment, so it’s upside down.

Spread the ice cream mixture evenly over the cookie and smooth the top.

Place the remaining cookie on top, right side up.

Freeze the ice cream cookie sandwich for about 8 hours, or until completely firm.

Once fully frozen, remove it from the freezer and cut into 12 squares.

You can either wrap them individually in wax or parchment paper and store them in the freezer for later, or place them in a freezer-safe bag, unwrapped.