In a large, heavy-bottomed pot or dutch oven melt 6 tbsp butter over medium high heat.
Add the onion and carrots and cook for 5 minutes. Add garlic and peas and cook for 1 minute more.
Add 3 tbsp of flour to the pot and stir to combine. Add evaporated milk and chicken stock. Stir to combine.
Bring the pot to a boil and add the chicken and thyme. Season with salt and pepper. Add 1 tbsp lemon juice. Let the soup simmer for about 10 minutes, uncovered, while you make the dumplings.
In a large bowl, whisk together the flour, baking powder, salt and thyme. Pour the milk and butter into the center of your bowl. Stir in the milk and butter until a soft dough forms.
Once your dough is formed, use a large cookie scoop or spoon to create balls of dough. Roll the dough gently into 9 - 10 balls.
Place the balls of dough onto the surface of the pot, taking care to place them around the pot and not overlapping if possible.
Press the dough balls down into the pot so that they are covered by the liquid.
Add the lid to your pot and reduce the heat to a simmer. Simmer for 15 minutes, until the dough is cooked through. Test a dough ball to see if it’s cooked through before removing the pot from the heat. If it’s not cooked through, keep simmering the pot for 3 - 4 more minutes.
When you roll the biscuits for the top of your pot pie it’s OK if they aren’t perfect balls. Gently form the balls, not pressing too hard, and then drop them into your pot.
You can substitute other vegetables if you like. Celery and mushrooms are popular additions.