emmmm, im no expert with them, but I think they are like ESTPs in that they just like seeing some kind of overt effort - physical effort to hang with them, talking to them etc. Not words but action oriented effort. Making time for them will probably go very far.
Do stuff for them, in a manner that indicates to them you care. That's the nice thing about ESJs that I have found, is that what they appreciate is usually pretty apparent and thus easy to do. For example, my ESJ really likes flowers, so if I mess up or for no reason at all I'll just send some to her work, because I know she equates flowers with apology or feeling, and she likes feeling successful. The public display always makes her feel better because she gets to tell people her bf got them for her, blah blah blah blah, girly girly stuff.
ESFJs want to feel needed (for what they do more so than who they are in my experience) and helpful. Let them know how much you appreciate the things they do for you and make them feel as though they are helping make your life better.
It also helps, like Jock says, to do nice things for them. I find that words are appreciated, but tangible things (gifts, time, effort) seem to hold the most weight - they are "don't tell me show me" people, imo.
"Be who you are and say what you feel because those who mind don't matter and those who matter don't mind. " - Dr. Seuss
I can't spell...get over it
Just tell her that you really enjoyed the pie she made for you when you were under the weather, and then say that you don't see how you could possibly live without that pie in your life, and ask for the recipe or for her to make it again some time.
The ESFJs I know tend to value tradition rather highly, so I imagine any of the 'usual' courting rituals and displays of affection would work well. As Jock said above - flowers are good, also things like cute post-it notes on the dashboard of her car, greeting cards, dinner reservations, etc. Aim to do obvious things for her, not just subtle things.
Make sure you tell them how much you appreciate their help and do something out of the blue for them. Since many of them love to help others, I think they secretly love it when others consider them or help them for a change.
EDIT: JoSunshine, I wrote down pretty much the exact same before I saw your post... lol