Dice potatoes into small chunks so they cook at the same rate as the other vegetables. Ensure all veg is chunky, not finely chopped.
Heat a pan over medium heat with oil. Add the diced onion and cook for 5–7 minutes until softened and starting to turn golden. Add the ginger, garlic, and red chilli, cooking for 1 minute until fragrant.
Add the cumin, ground coriander, cinnamon, and tomato paste to the onion mixture. Stir constantly for 60 seconds to "bloom" the spices, allowing them to release their oils. If it looks too dry, add a tiny splash of water to prevent burning.
Add the diced potatoes, cauliflower florets, and red pepper to the pan. Stir well for 2-3 minutes to coat all vegetables in the spice paste. Pour in the canned tomatoes and vegetable stock. Bring to a boil, then immediately reduce to a low simmer.
Stir in the green beans and courgette (this ensures they stay al-dente). Simmer uncovered for another 5–10 minutes, stirring occasionally, until the potatoes are tender and the sauce has reduced and thickened.
Stir in the garam masala right at the end (this preserves its aroma), season with salt to taste, and garnish generously with fresh coriander.