I've heard it said many times that Lubavitch hasidim learn chassidus like it's gemara. It's easy enough to see what an advanced gemara shiur looks like, being something that presupposes a familiarity with the style and structure (and to an extent, the content) of the Talmud's commentaries and meta-commentaries - but what does an advanced shiur in Sefer Tanya look like? I'm not claiming to be at an advanced level (I'm definitely not); I'd just like to know what it means to learn chassidus "like it's gemara". Can be Hebrew or English.
When a beginner learns Gemara, one of the greatest setbacks is the lack of "prerequisite" knowledge. Many concepts are preestablished, including the 13 middos of learning Torah (gzeira shava, binyan av etc. etc.), and even more so there are different styles of sugiyos, how a question is established, how a terutz is attempted and so on.
The seasoned learner will be able to run through a page of Gemara, quickly recognizing through the nuances in the language what exactly is going on. Of course, today we have the Kehati Mishnayos to help us get much of the prerequisite knowledge for understanding a sugiya prior to learning it--much like a hakdama to a shiyur.
And then there's another, deeper level of Gemara learning, which is where the iyun comes in. Deep knowledge (characterized by a detailed, broad understanding) of various other masechtot will deepen one's understanding of other masechtot. Suddenly Tosfos will take on a new light, (rather than have to look up the masechet that Tosfos is referring to, you'll already know exactly what he's talking about, and his question will ring clearly in your head, arousing more questions which will prompt your delving into the sea of meforshim.
The above is what I would consider a sample of what learning Gemara be'iyun should look like (although there are, of course, many styles...the above is only a partial example, perhaps of the Chabad style of learning Gemara--since that is what I am familiar with).
So now, here is the parallel, Chassidus version (don't worry it's not as long--I'll summarize):
In Chassidus, there are dozens (if not hundreds...) of concepts. Much like the various styles of sugiyos mentioned above in Gemara, there are types of concepts which force one to think in slightly abstract (but very practical) concepts. Like with Kehati, there are books explaining the different concepts on their own, and often these books (as well as books explaining specific Chassidic works--Chassidus Mevoeres notably among them) are essential for anyone attempting to learning on their own (in a way similar to Schottenstein Gemaras).
A seasoned student of Chassidus will have been trained in Chassidic thought--a glance at a maamar (a technical term for a work of Chassidus) will show him what type it is, what concepts are being discussed, and what new depth to look for.
An advanced shiyur, then, like the ones mentioned above, by R' Yoel Kahn, will assume the listener has been conditioned to a deep style of thinking. Anyone else can of course listen, and not understand what all the storm is about... (By the way, the majority of online shiyurim by R' Yoel Kahn can be found on http://otzerhachassidus.com and chassidus.com).
But all in all, I think the following is the most important point of all, in response to the question: Like in Gemara, a learner of any level in Chassidus, is expected to understand fully well what the text means before continuing onwards. It happens all too often that someone will consider himself (or is considered) very knowledgeable in Chassidus (there is no lack of rabbis who fit this example), when in fact all they know is words and how to say the technical explanation of concepts by heart from all sorts of sources (like texbook answers). But in reality the depth of understanding is totally lacking.
Someone who truly learns Gemara, for example, can't run through the page--Rashi, Tosfos and all--and really believe that he fully understood the first time! He must examine the page one line at a time, see if he really got it, ask a question, examine the response, see if he really understood that Rashi, and sometimes realize that he has an essential misunderstanding since the very beginning of the page!
Likewise, when learning Chassidus, the learner must examine every line; ask; ponder; consider; reject!; consider again...and so on. This is called Chassidus be'iyun, and learning for a few years in this manner has a substantial, deep rooted impact on the person. Relearning old works with newly acquired knowledge gains brand new depth, almost every single time they are revisited....
The Yiddish Shurim cover almost all of Tanya and are available here.
His students are compiling them into Hebrew in print (written about here).
https://insidechassidus.org/tanya There are different levels here.
He also has shuirim on many topics in chassidus and hashkafa
All are in english