Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking pan with baking spray and parchment paper.

In a medium bowl, whisk together the flour, baking soda, cinnamon, and salt until well combined.

In a large bowl, cream the butter and brown sugar until light and fluffy, about 2-3 minutes.

Add the eggs one at a time, blending well after each addition, and pour in the vanilla extract.

Gradually mix the dry ingredients into the creamed mixture until just combined, then fold in the oats and raisins.

Spread the cookie dough evenly into the prepared baking pan, adding extra raisins on top if desired.

Bake for 18-20 minutes, until edges are golden brown and center feels set.

Let the bars cool in the pan for 5-10 minutes, then lift out using parchment to cool completely on a wire rack.

For the frosting, beat the softened butter, then gradually add the powdered sugar, maple syrup, heavy cream, and cinnamon until creamy.

Once cooled, generously frost the bars and slice into squares to serve.