• Preheat the oven to 375 degrees.

For the filling

• Stir together the brown sugar, cornstarch, and cinnamon in a small bowl.
• Place the plums in a large bowl and sprinkle the brown sugar mixture over, stirring to blend. Add the lemon juice and butter pieces and stir to combine.
• Transfer the plum mixture to a shallow 3 quart baking dish.

For the topping

• Put aside 1/4 cup of the sliced almonds.
• In a food processor, use on/off pulses to combine the granulated sugar, flour, salt, and 1/2 cup of the sliced almonds until the nuts are ground rather finely.
• Add the beaten egg to the flour-nut mixture and use on/off pulses to combine.
• Spoon the flour-nut-egg mixture over the plum filling. Top the crust with the remaining 1/4 cup of sliced almonds.
• Bake the crisp for 50-55 minutes, or until the top is golden and bubbling.
• Cool the crisp on a rack. Serve warm or at room temperature