Preheat oven to 350. Line a 9x13 pan with parchment paper and place the pan on a baking sheet.

To make the oatmeal layer
Whisk together the flour, baking soda, salt and cinnamon.

Beat the butter on medium speed until it is soft and creamy. Add the brown sugar and beat for 2 minutes, then add the eggs, one at a time, beating after each one. Beat in the vanilla. Reduce the mixer speed to low and add the dry ingredients, mixing just until they disappear. Still on low speed, or working by hand with a rubber spatula, stir in the oats and chopped peanuts.

Set aside 1 1/2 cups of the mixture, then turn the remaining dough into the buttered pan. Gently and evenly press the dough over the bottom of the pan. Set aside while you prepare the next layer.

To make the chocolate layer
Put the condensed milk, chocolate chips, butter, and salt in a bowl over a saucepan of simmering water and stir occasionally until the milk is warm and the chocolate and butter are melted. Remove the bowl from the pan of water and stir in the vanilla, raisins, and peanuts.

Pour the warm chocolate over the oatmeal crust, then scatter the remaining oatmeal mixture over the top.

Bake for 25 to 30 minutes, or until the topping is golden brown and the chocolate layer is dull and starting to come away from the sides of the pan. Transfer the baking pan to a rack and cool for about 2 hours.

Using the parchment paper, pull the bars out of their pan and place on a rack. Refrigerate for at least 1 hour before cutting.