In a large bowl, place the popcorn, raisins, walnuts and steel cut oats.
In a saucepan over low heat, heat the honey, molasses, vanilla, cinnamon and 1 tablespoon butter together just until melted. Pour this mixture over the popcorn mixture and mix well.
In the same saucepan over medium-low heat, melt 1 1/2 tablespoons butter and the marshmallows, stirring constantly until the marshmallows are melted. Add in 1/2 teaspoon cinnamon and mix. Pour this mixture over the popcorn and mix well.
Press the popcorn mixture into an 8x8 pan that has been lined with wax paper. Rub a bit of butter on your fingers and press firmly on the mixture to completely cover the bottom of the pan. Sprinkle the additional 3 tablespoons of steel cut oats on top of the bars and press them in lightly with your hands.
If desired, melt 1/4 cup white chocolate over low heat on a double boiler. Drizzle the melted white chocolate overtop the bars. Cut into 16 bars.