Trim the rind from the bacon and cut into 1 inch cubes. Place bacon in a large, deep skillet. Cook over medium high heat until brown and crispy. Cover and reduce heat to lowest setting to keep bacon warm.
In a small, dry skillet, toast curry powder over medium heat, stirring often, until fragrant, about 30 seconds. Remove from heat.
In a medium bowl, whisk together the vinegar and mustard. Add oil in a thin stream, whisking constantly, until the oil is completely incorporated. Add curry powder and whisk until smooth. Season to taste with salt and pepper.
In a large bowl, toss together the bacon, spinach, mushrooms and vinaigrette until evenly coated. Adjust salt and pepper to taste and serve immediately.
