Bring chicken stock to boil in a 2 qt sauce pan over high heat. Reduce heat and keep at a bare simmer.
In another 2 quart saucepan, heat butter and oil and add onion, cooking until translucent. Add rice and stir to coat evenly with butter/oil mixture.
Slowly add hot stock to rice, 2/3 cup at a time, stirring constantly until rice absorbs the liquid, 4 to 5 minutes for each addition.
When all the liquid has been absorbed, pour risotto out onto a large baking sheet to stop the cooking and cool as quickly as possible. Refrigerate uncovered until cold. Can store in covered container up to 2 days before finishing.
Work with remaining ingredients. Bring stock to boil.
Place chilled risotto in 4 qt sauce pan over medium heat. Pour 1-1/2 cups boiling stock into risotto, stirring constantly with a wooden spoon. Continue cooking until rice is just barely tender.
Stir in cheese and butter, adjusting consistency with more stock if risotto becomes too thick.
Season salt and coarse pepper. Remove from heat and add lemon and zest. Serve with garnish of choice.