Preheat the oven to 400 degrees F.

Heat the butter over medium-low heat in a large (12-inch) oven-safe skillet or dutch oven. Once melted, add in the onions, carrots, celery and garlic with a big pinch of salt and pepper. Cook, stirring often, until softened, about 5 to 6 minutes.

Sprinkle the flour all over the veggies and stir. Cook, stirring often, until the flour toasts and becomes fragrant and golden, about 5 more minutes.

Slowly stream in the chicken stock while stirring the whole time. It should thicken as you stir. Bring the mixture to a boil then reduce it to a simmer. Add the chicken in. Continue to cook and simmer until it thickens.

While the filling is cooking, whisk together the flour, baking soda and salt in a large bowl. Add in the butter pieces and use a pastry blender, fork or your fingers to cut the butter into the dough. You want the butter equally distributed throughout the flour - try to do this somewhat quickly so it doesn’t get too warm.

Stream in the cream and bring the dough together with a fork, bringing it together more with your hands. You want all pieces of the dough moistened. If needed, you can sprinkle in a bit more cream. You don’t want a ball of dough though - keep it in pieces like a crumbly topping!

Turn the heat off under the chicken filling. Sprinkle the crumble on top. Place the pan in the oven and bake for 15 to 20 minutes, or until it is golden brown on top.

Remove from the oven and let cool slightly. Serve!