Line an 8- by 8-inch baking pan with parchment paper.
Grind the peanuts, brown sugar and flour in a food processor. Slowly add the sweetened condensed milk until the mixture starts to come together. Check if the mixture is ready by taking a handful and pressing it into a ball with your fingers. The mixture should hold its shape. If it doesn't, add more sweetened condensed milk to achieve desired consistency. Turn out onto the prepared pan. Firmly press down on the mixture until it is level and compact. Let the mixture set up at room temperature for 1 to 2 hours.
Turn out the candy onto a cutting board and lift away the parchment paper. Cut into bite-size squares. Serve on desired platter and garnish with chopped peanuts. Store in an airtight container.