Preheat oven to 350 degrees. Cook the orzo for 8 to 10 minutes or according to package directions. Drain and toss with butter and currants and spread in a shallow 2 quart gratin dish; set aside. Add sugar and saffron to milk and bring just to under a boil and cool. Whisk eggs together and gradually blend in milk; season with a pinch of salt and lots of fresh pepper. Pour over pasta and currants. Place gratin dish in a large baking pan and pour boiling or very hot water into the pan to reach half way up the side of the gratin dish. Bake for 1 hour or until set.