Slice the three large peaches into baked pie shell. If the peaches are very juicy, lightly brush the pie shell with soft butter before adding peaches. In a small saucepan, mash the soft peaches; add sugar, cornstarch, and water. Cook over medium heat to boiling point, stirring constantly. Boil 1 minute, or until thick and clear. Remove from heat and add almond extract and butter. Pour over peaches in pie shell and chill for several hours until set. Serve with whipped cream, if desired.