In a high straight-sided medium skillet, melt the butter over medium-high heat. Add the shallots and the garlic, and cook until shallots are lightly browned, 2 to 3 minutes.
Stir in ginger, cumin, and turmeric, and cook for 30 seconds. Add spinach and mustard seeds; season with salt and pepper; cook, tossing until spinach is just wilted, 1 to 2 minutes. Remove from skillet, and serve immediately.