Preheat oven to 400 degrees. Grease a pie dish and roll out defrosted pie crust, spreading it out so it reaches all sides.
Mix all ingredients together in a small bowl, except the reserved two plums for the topping.
Spread the filling onto the pie crust, leaving about a one inch space around the edges.
Fold the edges of the pie crust over two inches so that it covers part of the filling, overlapping as needed.
Slice the remaining two plums and arrange in the middle of the galette.
Beat the egg with a tiny bit of water in a small bowl and brush the pie crust with the egg wash.
Cook in the oven for 30 minutes. Let cool for 10 minutes. Drizzle with honey before serving.
Notes
I still had a lot of the egg wash leftover, so I saved it in a glass Tupperware and made scrambled eggs for breakfast the next morning! You can also spray the pie crust with coconut oil spray instead of the egg wash.