You'll get plenty of Health and Flower Point-restoring items in Paper Mario: The Thousand-Year Door, but the ones that give you more HP/FP usually can't be bought. Aside from the Jammin' Jelly and Ultra Mushroom, you won't find too many items that restore more than 15 HP/FP. Cooking will give you items that are ideal for recovering your energy in battle. You can create stronger meals by cooking up easy-to-find and/or cheap ingredients, such as a Mushroom. One recipe to consider is Inky Sauce, a juice that doesn't look very appetizing, but it's simple to cook and recovers a fair amount of FP.