Over medium heat, add olive oil to a medium saucepan. Add leeks and garlic and cook 1-2 minutes. Add crimini mushrooms; cook 3 minutes or until mushrooms soften slightly. Stir in rice; cook until rice becomes slightly translucent, stirring occasionally, about 4 minutes. Rice may brown slightly.
Stir in chicken stock and bring to a boil. Add salt; reduce heat to medium-low. Cover and cook 45-50 minutes or until rice is tender. Stir in pepper and add more salt to taste.