Filling: Combine margarine, chocolate chips, evaporated milk, chocolate flavoring, and cornstarch in saucepan.
Stir to completely dissolve cornstarch.
Place saucepan over medium heat, and stir until mixture comes to a full rolling boil.
Remove from heat.
Stir occasionally until mixture has cooled.
Base: Cream margarine, fructose, and sugar
Beat in egg and vanilla extract.
Add flour and baking soda.
Beat well.
Blend in 3/4 cup (440 mL) of the oatmeal.
Press three-fourths of the base mixture into the bottom of a 9 x 9 in. (23 x 23 cm) shiny baking pan.
Spread with cooled chocolate filling.
Add remaining 1/4 cup (60 mL) of the oatmeal to the remaining base mixture.
Crumb with a fork or your hands.
Sprinkle crumb mixture over cookie surface.
Bake at 350°F (175°C) for 25 to 30 minutes.
Cool on cooling rack.
Cut into 36 bars.