Copper conducts heat roughly four times better than aluminium. In practice that means water comes to a boil faster, milk sauce does not burn at the edge while the centre is still cool, and you can actually lower the temperature when needed without waiting.
The CopperBond saucepan has five layers: 18/10 stainless steel against the food, then copper, then aluminium, then copper again, and finally a layer of magnetic steel that makes it induction-safe. Handmade in Italy, with a stainless steel lid and lifetime guarantee. This is the cookware Thomas Keller chose for The French Laundry and Per Se. Available in 1.4, 1.9, 2.8 and 3.8 litres. Hand-washing recommended.