Here's the list of favorite foods for every characters, even the non-romanceable ones:
Claire: Omelette rice: rice, egg, tomato
Lorna: Fruit tart: strawberry, blueberry, cookies, horse milk
Mira: Tomato salad: tomato, onion, cabbage
Evie: Corn soup: corn, horse milk
Grace: Pumpkin soup: pumpkin, horse milk
Iris: Brandy ice cream: horse milk, cherry, fairy egg, liquor
Adele: Oden: japanese white radish, carrot, mushroom, potato
Aria: Curry rice: rice, potato, onion, meat
Minya: Gratin: cheese, flour, horse milk, broccoli
Katia: Pudding: fairy egg, milk
Isabel: Hamburger: meat, onion, carrot, broccoli
Natalie: Meuniere: fish, flour, lemon, cabbage
Harry: Grilled fish: fish, japanese white radish, lemon
Aleisha: Cheese soufflé: cheese, flour, egg
Elaine: Pancake: butter, flour, fairy egg
Rosetta: Pizza: flour, tomato, asparagus, cheese
Liliel: Ice cream: horse milk, fairy egg
Gordon: Beef bowl: meat, rice, onion, egg
Cynthia: Sukiyaki: meat, mushroom, green onion, egg
Kate: Orange Jelly: orange, cherry, fairy egg
You only need one of these ingredients for each dish, but keep hoarding at least 10 of each just to be sure.