Bring stock and 2 cups water to a simmer in a medium saucepan (do not boil). Keep warm over low heat.
Cook bacon in a large nonstick skillet over medium heat until crisp. Remove bacon from pan; crumble. Add oil to pan; swirl to coat. Add leek, shallots, thyme, and garlic to pan; sauté 4 minutes or until tender. Stir in rice; cook 2 minutes. Stir in 1/2 cup stock mixture; cook 5 minutes or until liquid is nearly absorbed, stirring constantly. Reserve 1/3 cup stock mixture. Add remaining stock mixture, 1/4 cup at a time, stirring constantly until liquid is absorbed before adding more (about 25 minutes total). Stir in lemon juice, butter, pepper, salt, and Parmigiano-Reggiano. Remove pan from heat. Stir in reserved 1/3 cup stock mixture. Sprinkle with reserved bacon and chopped parsley. Serve immediately.