Pour 6 cups of water into a pot and bring to a simmer.
Heat the butter in another pot over medium-high heat and saute the shallots for 2 minutes. Do not let them brown. Add the rice and stir well, then cook for 2 minutes, stirring often, until the rice is well coated and hot.
Pour in the white wine and bring to a strong boil. Stir often and let this cook down. When it is almost dry, pour in 2 ladles' worth of the simmering water and sprinkle about a teaspoon of salt over the rice. Stir constantly until this has almost boiled away.
Add 2 more ladles' worth of the water and continue. Repeat until the rice is al dente. Taste for salt and add some if needed. Pour in a little more water and stir in the Parmigiano Reggiano cheese. Let this cook for 1 to 2 minutes, stirring often.
Turn off the heat and stir in the truffle oil. Use as much as you want, but at least a couple tablespoons. I would not use more than 3 tablespoons, though.
Serve in shallow bowls and shave the truffle over the top at the last moment.