In a microwave, melt peanut butter chips with milk; stir until smooth. Pour into a foil-lined and greased 9-in. square pan. Cool completely at room temperature. Lift out of the pan and invert onto a cutting board.
Remove foil; cut into 3-in. x 1/4-in. strips. Fold muffin cup liners in half, pressing out creases; fold in half again. Fold point under; use as holder for fries. Use icing for ketchup if desired.