Heat olive oil and butter in a large Dutch oven over medium heat. Add onion, carrots, and celery. Cook for about five minutes until the vegetables soften and smell sweet.

Add minced garlic to the pot. Stir for one minute. Sprinkle flour over the vegetables. Stir constantly so the flour coats everything evenly and cooks lightly.

Slowly pour chicken broth while stirring. This prevents lumps in the sauce. The mixture will start thickening and forming a smooth base for the stew.

Pour in the milk and mix well. Add salt, pepper, and thyme. Let the stew simmer gently for ten minutes until creamy and rich.

Stir in shredded chicken and frozen peas. Cook for another five minutes. The chicken warms through and the peas stay bright green.

Preheat your oven to 400°F (200°C). The biscuits will bake on top of the stew and turn golden brown.

In a bowl mix flour, baking powder, salt, and sugar. Add cold butter cubes. Use your fingers or a pastry cutter to mix until crumbly.

Pour buttermilk slowly into the flour mixture. Stir gently until a soft dough forms. Do not overmix or the biscuits may become tough.

Lightly flour your surface. Roll the dough about one inch thick. Cut biscuits using a cutter or glass.

Carefully place the biscuit rounds on top of the hot stew. Leave a little space between them.

Transfer the Dutch oven to the oven. Bake for about twenty minutes until the biscuits turn golden brown and fluffy.

Remove from the oven and let it sit for five minutes. The stew thickens slightly and becomes easier to serve.