In a pan, brown ground beef over medium heat. While cooking use a spoon to make the pieces of beef as small as possible. Add onion and frozen peas and carrots. Cook 3 minutes.
Add potatoes. Stir in chili powder, turmeric and garam masala. Pour water over the top and continue cooking for 3-4 minutes or until water is absorbed. Stirring occasionally. Remove from heat.
Roll puff pastry into a 18" x 12 inches rectangle. Cut into 8 even rectangles. Place 2 tablespoons of mixture in the center of each rectangle. Fold one side over the top of the filling and bring it to the other side. Use a fork to press down edges to seal. Brush each samosa with egg wash. Sprinkle with kosher salt.
Spray a baking sheet with non-stick spray or line sheet with parchment paper. Place filled samosas on the prepared sheet. Bake for 12-15 minutes or until golden brown.