Preheat the oven to 375F.
Lightly butter the bottom and side of a single-serve ramekin.
Roll out the pie crust dough and cut into two circles — one should be large enough to line the inside of the ramekin; the other, a little wider than the diameter of the ramekin.
Take the bigger circle of dough and fit inside the ramekin.
Mix together the vegetables, yogurt and herbs. Season with salt and pepper.
Spoon the filling into the crust-lined ramekin. Sprinkle the pieces of cold butter on top.
Cover the ramekin with the smaller circle of crust. Tuck or just press against the sides to seal.
Pierce the top crust with a fork in several places to create steam vents.
Blush the top crust with beaten egg.
Bake at 375F for 25 to 35 minutes or until the top crust is lightly browned.