Bring the stock to a boil in a medium saucepan, cover, and keep warm over low heat.
Heat the butter and olive in a large saucepan.
Saute the leek and shallots over medium high heat, stirring occasionally, until translucent, about 5 - 7 minutes. Add the arborio and white rice to the leek/shallot mixture and sauté, stirring constantly, for 2 minutes.
Reduce the heat to medium low, add 1 cup of the hot stock and stir frequently until absorbed.
Continue adding 1 cup of stock at a time, stirring, and waiting for it to be absorbed before adding the next measure. This will take 25-30 minutes.
Remove from heat and stir in the lemon zest, fresh lemon juice and the parmesan cheese.