You can make this all at once in a pot, or in individual pie pans/ramekins. These directions are for individual, but that only matters on the last step, and all you're doing is waiting on the puffed pastry to do it's thing at that point.

Chop chuck roast into bite sized pieces. You could shred, but chopped is more rustic.

Add in a pot with vegetables and broth and allow everything to come up to temp (this assumes your meat and veggies are cold)

Remove meat and veggies and add fresh herbs as whole pieces

Simmer for about 10 minutes, then remove the herbs

Mix together cornstarch and 1 T of cold water. Stir into broth and cook until desired thickness for gravy.

Stir in the meat and vegetables.

Spoon into desired cooking utensil

Cut puff pastry to barely fit, do not plan for pinching or sealing, this pie needs venting

Place pastry on top

If make as one large dish add a steam slit in the middle

Back at 425 until pastry is golden