Preheat the oven to 425-degrees F and butter a 9×13 baking dish.
Peel and dice the potatoes and carrots.
Boil the potatoes and carrots for 5-8 minutes. Drain and set aside.
In a large skillet, melt the butter, and cook the onions and garlic until tender.
After that, whisk in the flour.
Continue whisking as you add the chicken stock and milk to make the roux.
Season the mixture with salt, pepper and tarragon OR thyme.
Mix all the vegetables and ham into the roux. Taste for seasoning.
Pour half of the ham pot pie filling into the bottom of the buttered baking dish.
Sprinkle half the cheddar cheese on top.
Add the rest of the filling and top with the remaining cheese.
Unroll the puff pastry on top of the filling and tuck the edges until. (There’s no waiting for your puff pastry to thaw and no need for flour or a rolling pin when you use Wewalka Puff Pastry. This is another reason I love it!)
Bake for 20-25 minutes until the puff pastry is golden brown and the filling is hot and bubbly.