Make the peanut butter layer by mixing together the peanut butter, almond or oat flour, maple syrup, and vanilla extract (if using) in a large bowl.
Transfer the peanut butter mixture to your prepared baking pan and press it into an even layer in the pan.
Make the chocolate layer by melting the chocolate chips and peanut butter in either the microwave or over a double boiler until completely smooth. Pour the melted chocolate mixture on top of the peanut butter layer and spread until it’s smooth and even.
Chill the bars in the freezer for one hour, then remove and slice into small bars.