Line an 8 x 8-inch or 9 x 9-inch square baking pan or glass baking dish with parchment paper.
Make the bars:
In a large bowl, mix the oats, cereal, salt, and raisins. Set aside.
In a small pot, melt the butter, syrup, and brown sugar. When it starts to boil, reduce the heat to medium-low, and cook for 4 minutes, making sure the mixture continues to minimally bubble while stirring often. Turn off the heat and add the vanilla.
Pour the liquid mixture into the dry mixture. Mix well to combine all ingredients.
Place the oaty mixture into the square baking dish. Cover with parchment paper, and press down with your hands until the mix is well packed. Just when you think you’ve pressed down enough, press some more!
Chill and slice:
Allow the pan to cool at room temperature for at least 2 hours.
Lift the parchment paper out onto a cutting board, and slice into 12 bars.
Storage:
After cutting the bars, store them in an airtight container or ziplock bag for up to 1 week in the pantry.