Place butter in a medium saucepan over medium-high heat. When the butter turns light brown in color, add shallots and stir for 10 seconds then season with salt and pepper. Add the sherry vinegar. Remove from heat, place in blender. Turn blender on high; slowly drizzle in olive oil to create an emulsion. Once all the olive oil is added, turn blender off. Taste for seasoning; adjust with salt and pepper, if needed. Add thyme and Italian parsley to blender, quickly pulse to incorporate.
In a large bowl, toss salad greens with vinaigrette and serve immediately.