Leftovers of risotto can be used in the most delicious Sicilian appetizer or lunch even, arancini, or can be transformed in a frittata, but never the following day (my personal opinion). So, store the leftover ( of course in a certain amount) in the freezer and defrost on time for the frittata.
Remember the pumpkin risotto with mozzarella, caramalized garlic, chestnuts served with pesto? Mix the defrosted risotto with 2 battered eggs, 100 ml of milk, 50 grams of grated pecorino (I used a real tasty one with truffle), 2 table spoons of pesto, pepper and salt. Put the mixture in a springform covered with a baking sheet. Bake in the oven at 180° for 30 mins. Serve with salad.