Preheat the oven to 350°. Prepare a baking sheet with a piece of parchment paper. Lay out the pie crust on top of the parchment paper.
Place the sliced apples in a bowl. Squeeze the juice from half a lemon over the apple slices and toss to mix. Next, sprinkle one tablespoon of flour over the center of the piecrust and layer the apple slices on top overlapping slightly. Sprinkle the apples with one tablespoon of sugar.
In a small bowl, sprinkle the strawberries with the second tablespoon of sugar and toss to coat. Layer the berries on top of the apples and dot the berries with cold butter cutting the butter into small pieces.
Fold up the edges of the piecrust over the apples and berries overlapping the crust as you go and leaving the center exposed. Brush the beaten egg wash on the crust and sprinkle the remaining tablespoon of sugar over the crust and bake the galette for 20 minutes or until the edges become golden brown.
Remove the galette from the oven and allow it to cool. Serve the dessert with vanilla ice cream.