There are a few things to keep in mind to avoid your sauteed spinach coming out biter. Smaller and lighter looking leaves (often baby spinach) will naturally have a less bitter taste than darker coloured and bigger leaves. The stems also contribute to bitterness in spinach so if you find they are overly long and thick, simply trim or tear them off before adding them to the pan. Finally, overcooking spinach will result in a more bitter dish. Keep a close eye while you're cooking and as soon as your leaves start to wilt, give it a few extra stirs then remove it from the heat. The minced garlic, good quality extra virgin olive oil and salt and pepper in this recipe for sauteed spinach will mask any lingering bitter taste.