In a medium saucepan, combine the rhubarb, strawberries and honey over medium-low heat. Simmer, 7 to 10 minutes, stirring occasionally or until the rhubarb is very tender and beginning to fall apart.
Remove the saucepan from the heat and stir in the seeds from half of the vanilla bean. Transfer the mixture to a fine mesh strainer set over a medium bowl. Press the mixture to remove excess liquid.
Heat the oven to 400°F and line two baking sheets with parchment paper; set aside. Unfold one of the puff pastry sheets onto a lightly floured work surface and press out into a square. Cut the puff pastry sheet into 4 equal squares; repeat with the remaining sheet.
Spoon a scant tablespoon of the rhubarb mixture into the center of the squares. Brush the edges of the pastry squares with a small amount of egg wash and then carefully fold the pastry squares in half diagonally to form triangles. Use a fork to seal the edges together and place the turnovers 2-inches apart on the prepared pans. Cut three small slits in the top of each turnover. Brush the tops of the pastries with the egg mixture and sprinkle with a pinch of sugar.
Bake 15 to 18 minutes or until the turnovers are golden brown and puffed. Meanwhile, in a small bowl, stir together the powdered sugar, milk and vanilla bean until smooth. Drizzle over the top of the turnovers; serve warm or at room temperture.