Cut the paneer into 1- to 1 1/2-inch cubes. Chop the onion and set aside. Chop the tomato and set aside separately. Scrape peel from the ginger with a spoon, and coarsely chop the ginger. Grind the ginger, garlic, and jalapeño into a coarse paste in a mini food processor, or finely chop. Trim roots and coarse part of stems from the spinach. Rinse spinach well and spin dry, then chop. Set ingredients aside.

Line a plate with paper towels. Heat the oil in a large nonstick frying pan over medium heat. Add the paneer and fry, turning occasionally, until light golden all over, 5-10 minutes. Transfer to the plate and set aside.

Heat the oil in a very large frying pan or Dutch oven over medium-high heat. Add the chopped onion and cook, stirring often, until slightly softened, about 8 minutes. Add the ginger-garlic paste and cook, stirring often, until slightly softened, about 30 seconds.

Add the coriander, salt, and chopped tomatoes and stir well. Reduce heat to medium and cook until tomatoes soften, about 10 minutes.

Increase heat to medium-high. Stir the spinach into masala paste (in batches, if needed, until it wilts) and cook, stirring occasionally, until leaves are wilted, stems are tender, and about half of the liquid cooks off, about 10 minutes.

In a food processor or high-power blender, blend the spinach and masala paste into a puree. Blend in batches if needed.

Return the puree to the frying pan. Stir in the garam masala, and paneer. Add the water, if needed for a looser texture. Cover and simmer over low heat until paneer is hot, about 5 minutes.

Stir in the heavy cream and simmer for 1 minute.

Serve the palak paneer with naan or rice.