In a bowl, combine rhubarb, strawberries, sugar, cornstarch, lemon juice and cinnamon.

On lightly floured surface, roll out half of the pastry and line a nine-inch pie plate.

Spoon in filling.

Roll out pastry for top crust; using pastry wheel or knife, cut into 1-inch wide strips.

Brush pastry rim with some of the beaten egg.

Gently weave strips over the pie to form lattice; trim and flute the edge.

Brush lattice with beaten egg. Sprinkle top with sugar if using.

Bake on a baking sheet with sides in a 425 degree Fahrenheit oven for 15 minutes. Tip: If you do not have a cookie sheet handy, make a drip catcher out of foil paper, larger than the bottom of the pie plate, and place it under the pie plate and up the sides loosely.

Reduce heat to 375 degrees Fahrenheit and bake for 50 to 60 minutes longer or until rhubarb is tender, filling thickened, and the crust is golden.

Let stand for 15 to 20 minutes before cutting.