Heat the olive oil in a large skillet over medium heat. Add the onion, carrots and celery with a pinch of salt and pepper, and cook for 5–6 minutes until softened.
Stir in the garlic, tomato paste, thyme, rosemary and paprika. Cook for 1-2 minutes, stirring constantly, until the tomato paste darkens slightly and becomes fragrant.
Transfer the vegetables to the slow cooker. Add the broth, Dijon, potatoes, butternut squash and bay leaves. Stir to combine.
Cover and cook on low for 6–7 hours or high for 3 hours, until the vegetables are fork-tender. For the best flavour and texture, cook this stew on low. The longer, gentler cook keeps the vegetables tender without turning mushy and allows more time for the flavours to develop. You can use high only when you're short on time or see the post for Instant Pot instructions.
Remove the bay leaves. For a thicker stew, blend about 2 cups of the cooked vegetables and broth (use an immersion blender, or transfer to a countertop blender), then stir the puree back in.
Stir in the chickpeas and green peas. Cover and let sit on warm for 10 minutes to heat through.
Stir in the lemon juice and parsley. Taste and season well with salt and pepper. Garnish with fresh dill, if desired.