To make Ginger-Garlic paste - throw garlic, ginger, and canola oil in mini food processor and process to semi-smooth paste. Mix Ginger-Garlic Paste with coriander, turmeric, and 1/2 cup water in small bowl. This is a simple wet masala (spice mix). Set aside. In a large pot, warm the oil over medium-high heat until shimmering but not smoking. Add the serrano pepper, wait 30 seconds, and then add the cumin seeds and wait until they're done spluttering. Add the wet masala (careful, it will also splutter). Cook until paste thickens, deepens in color slightly, and oil oozes out of the perimeter of the masala, about 2 minutes. Add cauliflower and potatoes, stirring to coat vegetables with masala. Season with salt and add 1/2 cup water. Cover and cook over medium heat 10 to 15 minutes. Then, remove lid, stir, and cook until the cauliflower and potatoes are cooked through, about 5 minutes. Garnish with cilantro and serve. A dollop of yogurt is good here too.