melt half of the butter in a large heavy skillet over medium heat. Add onion and cook 3 to 4 minutes or until tender.
stir in orzo and cook 1 minute. Add wine and allow wine to evaporate (approximately 2 minutes). Slowly add chicken broth, stirring constantly. cook about 8-10 minutes or until orzo is tender, stirring constantly.
remove from heat stir in remaining butter and parmigiano cheese.
season to taste with salt and top with thinly shaved truffles. Serve immediately.