1. You have some metal ingots.
2. You pulverize or macerate them all (using Thermal Expansion, or VoidCraft, or whatever) into dust.
3. You smelt all the dust in a normal furnace.
4. You have a Level Up! 2 skill that says you get a Y% chance of getting 2 items instead of 1, so you end up with more metal than you started with.

Not limited to metal, of course. Anything that you can pulverize, smelt, then pulverize again, then smelt again... Will work with this.