Combine the ginger, garlic, spices, lime juice and 3-4 tablespoons of water to make a medium-thick paste. Stir well, and add to a large pot. Let the spice paste sit over medium to high heat until just fragrant.
Add the cauliflower florets and potato, stirring well so that the vegetables are coated well with the paste. Cover and cook, stirring occasionally and adding water in 2-tablespoon increments if the mixture starts to stick.
Cook mixture about 30-40 minutes, until potatoes are soft. Garnish with cilantro and a lime wedge, and serve, if desired, with basmati rice or hot roti.