Preheat oven to 180 degrees C. Grease baking trays.
In a medium bowl, cream together the peanut butter, margarine and brown sugar. Stir in the egg, milk and almond essence. Sift together the plain flour, rye flour, bicarb soda and salt, add to the creamed mixture and mix until just combined. Finally, stir in the chocolate chips and mini marshmallows.
Drop biscuits by rounded teaspoonfuls onto the prepared baking trays. Bake for 8 to 10 minutes in the preheated oven or until golden brown. Allow biscuits to cool for 1 minute on the baking trays before removing to wire racks to cool completely.