I think what your friend said was:

Si tu mangeais ça, tu l’aimerais.

Which is an imperfect tense followed by a past conditionnal tense.

Both of these tenses sound very similar with regular verbs, so they often get blended together. But these are regularly used informal structures.

A more formal version, which makes the tenses slightly more discernable, is:

Si tu avais mangé ça, tu l’aurais aimé.

The problem is not the grammar but the semantics; it is perfectly correct to use two consecutive conditionals, provided the actions correspond; for instance, these sentences are normal;

• Tu la connaitrais tu en parlerais autrement.
• Vous arriveriez de bonne heure vous auriez de meilleures places.
• Le temps serait au beau nous vous inviterions à la campagne.

In “Tu mangerais ça tu l’aimerais bien !” there is a misundertanding between three actions that the verb can express: “manger” as a one time action and “manger” as “being used to eat sth”, “eating willingly sth usually”, and then another to be reckoned with later. If we choose the first possibility we get nonsense because the condition of liking something is not a natural consequence of the act of using it; this is quite analogous to the situation conferred by the sentence “If you would wear red dresses you would like red dresses.”. Supposing you are a woman you’ll say “Well, if I do wear them, of course that’s because I like them and again if I’ve never liked red I don’t see how wearing a red dress is going to make me like red”. So the semantics, what’s been intended as a message, is dubious. If we choose the second meaning we get also nonsense and that’s obvious because, since the person is used to eating whatever it is we’re talking about, that must be because they like it. The syntax then must be changed to give meaning to the sentence. The idea is that you must not consider the action as fully performed: the idea of having eaten of something fully, as in a meal, is wrong, instead the idea must be that of “eating some”; that is not communicated by the form given; to make the difference clear we add usual words to the form;

• Tu en mangerais tu l’aimerais bien ! (much as “Tu y goutterais tu l’aimerais bien !)
• Tu mangerais de ça tu l’aimerais bien ! (other possibility, according to variations in the context)

Those forms are however still not a very good choice as they are also used to mean “being used to eat sth”, eating willingly sth usually”.

• — I’ve got strawberry preserve and toast, do you eat that?
  — J’ai de la confiture de fraise et du pain grillé, vous en mangez ? (Vous mangez de ça ?)
  — Oui, j’en mange.

In the end, even if the corrected sentences are valid and can be used to communicate the same idea, it is more expressive, because clearer, to say this;

• Tu en/y gouterais tu l’aimerais bien ! or
• Tu l’essaierais tu l’aimerais bien !