Heat olive oil in a skillet over medium heat. Add onion, potatoes, salt, pepper, thyme, and rosemary. Cook, stirring occasionally, for 5 minutes or until onions are translucent and potatoes are softened. Add frozen peas, corn, and carrots.
Add beef broth; bring to a simmer. Fold flour into the mixture until integrated. The mixture should thicken. Add brisket. Cook for 5 minutes or until all ingredients are heated through. Remove from heat.
Cut raw pie crusts into circles approximately 5 inches in diameter. Fill the center of each crust with the potato mixture. Do not overstuff - you will have some mixture leftover. Fold over the crusts to create a half-circle and press the edges together with your fingers. Decorate the edges by pressing with a fork, if desired. Brush the top of each pie with melted butter.
Line each hand pie evenly over the prepared baking sheet and bake for 10 minutes or until crusts are golden brown.
Notes
When adding the beef broth and flour, I like to push the vegetables aside first and add to an empty section of the skillet, then slowly pull the vegetables back in once the roux is underway.