Preheat oven to 375° F.
Blind bake the pie crust by lining with parchment paper and filling with pie weights, dried beans, or granulated sugar. Bake for 15-20 minutes, until the edges are just beginning to set. Remove from the oven and carefully lift out the parchment and weights.
In a large skillet or sauté pan over medium heat, melt the butter. Add the onion and cook for 3-4 minutes, until softened.
Add the garlic, potatoes, carrots, celery, and peas and cook for 8-10 minutes, stirring occasionally, until the vegetables are just tender but not browned.
Sprinkle the flour over the vegetables and stir to coat. Cook for 1 minute to remove the raw flour taste.
Slowly pour in the vegetable broth, stirring or whisking constantly, and cook for 3-5 minutes, until the mixture thickens into a creamy sauce.
Add the chickpeas and stir until evenly incorporated.
Season with spices, then adjust salt and pepper to taste.
Spoon the filling into the partially baked pie crust and spread it into an even layer.
Bake for 30-40 minutes, until the crust is lightly golden. Let the pie rest for 15-20 minutes before slicing and serving.