I'd ignore it, and I wouldn't ask her if he's cute - that puts too much emphasis on looks. Kids start early with body image problems. Same goes for talk about "boyfriends" - they are too little to understand this. Believe me, at 9 and 10 when they want to "go out with boyfriends" you won't be happy that this conversation has been going on for years! Talking about boyfriends/girlfriends just encourages the crush, you know?
She doesn't know what she's doing with this - she's too young to really have these feelings, so she's just going by what she sees on TV and hears about on the bus. So I'd let her have the first call - if you hold back, it becomes even more intriguing. She doesn't have a cell phone so she's using the home phone. You could listen in on the other line for now. If he calls back again and again, you can answer yourself, be VERY POLITE (teaching kdis about manners is good!), and say she is too busy right now.
On the candy issue, tell her it's not polite to accept a lot of gifts from someone without reciprocating, and that he should not be spending his money like that. Also tell her if the school has a "no food sharing" policy - a lot of kids have allergies and so there is a "no sharing/no sneaking" policy that is important for health. If one kid sees this boy doing it and gives a problem food to another child, there's a safety issue.
You can also call his parents (perhaps after the kids go to bed) and make sure they know what he's doing. I would treat it like it's harmless and that it will probably burn itself out, but that parents should know what their kids are up to. Make sure you tell them you want to know if she calls their son - so it's not like you're suggesting they are bad parents and have this predatory son on their hands.
Make sure that she knows not to go off with anyone (not just this boy).
It's nice to know that your daughter is making new friends, so it's okay for you to enjoy that. It's okay that she learns to have phone conversations, to use good manners when making and receiving calls, and so on. You can use this boy's behavior as a teaching tool. For example, when he calls, does he give his name and say please may he speak to your daughter, or does he just say "Is Susie there?" Don't put him down, but DO say that this reminds you it's time to teach all kids her age the right way to speak and how to show they are old enough and mature enough to make phone calls - and teach her the etiquette of being polite to adults.
Otherwise I would completely, totally drop the discussion of "boyfriend" and "good looks" - that's not how you want her to evaluate people, is it? That's not how you want her to be viewed by others - based on her looks - is it? The cuteness factor wears off very quickly when kids are 10 and 12 and they start to engage in behaviors and have the ability to sneak behind your back. Then it becomes either dangerous or negative. You don't want to teach your daughter to be excessively flattered by the attentions of someone else, or to have to explain to you that things are just on a friendly basis. You want kids going on large group activities at least until they are 15!! And you don't want your daughter to be lured by the promise of candy at 6 and then maybe something more as she grows older.
I'd be much more nonchalant about it now, teach manners, and avoid the nuisance factor of multiple calls.