Step 1

Preheat the oven to 400 degrees F.

Step 2

Grease a 7x11-inch baking dish.

Step 3

In a large saucepan, heat 1/3 cup of the butter over medium heat.

Step 4

Add the mushrooms, the carrots, and the onion and cook, stirring, until tender, about 5 minutes.

Step 5

Stir in 1/4 cup of the flour until blended and the raw flour smell disappears, about 1 minute.

Step 6

Gradually stir in the broth and 1 cup of the milk.

Step 7

Bring the mixture to a boil, stirring constantly.

Step 8

Cook and stir until thickened, about 2 minutes.

Step 9

Stir in the chicken, the peas, the pimientos, and 1/2 teaspoon of the salt and cook until heated through.

Step 10

Transfer the mixture to the prepared baking dish.

Step 11

In a large bowl, whisk 2 cups of the remaining flour, the baking powder, the sugar, the remaining salt, and the cream of tartar.

Step 12

Cut the remaining cold butter into the mixture until it resembles coarse crumbs.

Step 13

Add the remaining milk to the mixture and stir until just moistened.

Step 14

Using the extra flour, lightly dust a work surface and turn the dough out onto it.

Step 15

Knead the dough gently, about 10 times.

Step 16

Pat or roll the dough to 1/2-inch thickness.

Step 17

Using the extra flour, lightly flour a 2 1/2-inch biscuit cutter, and then cut the dough.

Step 18

Place the biscuits over the chicken mixture.

Step 19

Bake, uncovered, until the biscuits are golden-brown, about 15-20 minutes.

Step 20

Serve.