Add 1 teaspoon butter and ¼ teaspoon olive oil to the same pan the apples were cooked in.
Stir in 1 cup arborio rice, saute for 3-5 minutes stirring occasionally to coat rice kernels
Begin making risotto by adding 1 cup of apple juice at a time to sauteed rice, allow liquid to absorb, and continue adding liquid 1 cup at a time, until all 4 cups are incorporated, this will take about 25 minutes. Risotto should be tender but not mushy, more liquid can be added if the rice is still tough, add 1 cup water until absorbed and test again until desired consistency.
Turn heat off.
Add cooked apples and celery and 1 teaspoon butter to risotto mixture, stir to combine. Finally, add ½ cup mayonnaise. Season with additional lemon juice, and salt to taste