• 2 tablespoons neutral oil such as grapeseed
• 1 onion (any colour), diced
• 1 5cm / 2 inch piece ginger, peeled and finely diced
• 3 garlic cloves, finely chopped
• 1 Serrano or other green chili, finely chopped
• 1 teaspoon ground cumin
• 1 teaspoon ground coriander
• 1 teaspoon garam masala
• 1 teaspoon turmeric
• 150 g French (puy) lentils
• 450 g (about 2 large) potatoes, peeled and cut into 2.5cm (1-inch) pieces
• 625 ml vegetable stock
• 1 (400ml / 13.5-ounces) coconut milk
• 3 rhubarb stalks (about 325g / 12 ounces), sliced into 1.25cm (1/2-inch) pieces
• Basmati rice, to serve (or other variety)

Curry leaf tadka (optional)

• 2 tablespoons ghee
• 1 teaspoon brown mustard seeds
• About 30-40 curry leaves
• Pinch of asafoetida