Step 1: Make the batter
For a 9" diameter pan, the low end would be about 8 4" pancakes, the high end about 13.
A 10" pan's useful range would be 10-16 4' pancakes.
Set your oven to 375 F. Making the batter is quick, and you want the oven to be ready to go in step 4. Now make the batter.
I use pancake mix, because I generally don't have milk and eggs on hand. If you don't use mix, thats cool too: do whatever you generally do to make pancake batter for however many pancakes you want to eat and skip to the next step.
For those of you who are using mix, err on the side of the batter being a little thin. I interpolate the measurements for numbers of pancakes off the chart on the back of the package: with a massive bag, the gradations of the chart are not fine enough, so this is somewhat necessary. I also convert the measurements to metric, but thats a matter of personal preference.
Step 2: The Pan
I use this large steel pan that is decidedly not non-stick. Its main advantage is that it is large, has high vertical walls and holds heat. It was also free, which is a major plus when finding cookware. Have someone else buy it for you, weddings are good for that. I believe this pan is about 9" in diameter, aim for something about the same size.
Put the pan on the range on medium heat. Krusteaz claims 375 degrees as medium heat, I just eyeball it. Put some butter in the middle off the pan; once it is all melted coat the bottom and lower sides of the pan with it. I have found a tablespoon to be about right, but it's up to your taste. So long as the batter won't stick to the pan you're golden. Non-stick spray is also an option.
***Feb 2011 Update:
I've been using this method for awhile now and at some point I realized using the range and the oven was silly. When you start the oven preheating, put the pan in there also. Take it out when the oven hits 375 (use an oven mitt), grease it, pour the batter in, and then put it back in the oven. The results are more consistent this way, since the pan is at the same temperature every time. ***
You don't want to burn the butter, so as soon as everything is hot* move on to the next step.
*Drop some batter in the butter; if it sizzles you are ready.
Step 3: Back to the batter
If you used as much butter as I do most of it will be on the edges now, displaced by the batter. Don't worry about it, it might make the edges funny but it wont hurt anything. Timing becomes important now. You want the underside to brown and cook, but not to get over done before you stick it in the oven. I test this by lifting the edge with a fork. If it hold its shape, and seems a little before you'd want to flip a normal pancake, thats when you want to cut the heat. Turn off the burner, open the oven, and stick the whole pan/pancake assembly in there.
Step 4: The Oven, and the Plate
Once it is done, pull the pan out of the oven, with an oven mitt. You will be going directly from the pan to a plate, so dexterity is somewhat vital. Place the plate upside down on top of the pan, and rotate the pan/plate assembly together so that the pan is upside-down on top of the plate. If all goes according to plan, the giant pancake will fall onto the plate with a minimum of fuss. If not, use a fork, or a few brisk taps to knock it lose. Hopefully it will end up looking something like the picture below.
Turn off the oven, and you can add whatever you like to the giant pancake. It is significantly thicker, which can make it something of a mouthful, but saves you all that time you would have spent making 10-12 dinky 4" pancakes. To find out just how much time (in theory), see the next step.
Step 5: Pancake Math
Changes in cooking time across the small range I'm using for this are more or less linear, and dependent primarily on pancake thickness. Of course, there are a lot of variables in this, and my very simplistic calculations are likely off by a significant margin of error. I'm OK with this because there are huge margins of error in cooking pancakes to start with.
Cooking 4" pancakes can be a massively parallel operation, if you have a large enough cooking surface. Thus, all pancakes in this operation takes the same time to cook, and cooking time is dependent on the number of pancakes you can cook at one time. Thus the number of pancakes you want (N), divided by the number you can cook at once (C), multiplied by the time it takes one 4" pancake to cook (t) yields the cooking time (T). As an equation this can be written thus: (N/C)*t=T Clearly, as C becomes smaller the cooking time approaches N*t, which is equivalent to cooking one pancake at a time until you to meet the required N.
Since the parallel method is inefficient when C is low, (which it is in my kitchen) a better solution is one that is serial, but has higher batch capacity. The one pan method processes pancakes one at a time, but can make them much larger and thicker. Cooking time in this system is related to the thickness of the pancake being made. As the thickness of the mega-pancake (D) increases above that of a standard pancake (d) cooking time will also increase. Again, expressing it as an equation: (D/d)*t=T.
The attached spreadsheet has cooking time comparisons between the two methods, and highlights the different effective range for different sized pans. A 6", 8", 9", and 12" pan are compared. All numbers in the spreadsheet are purely theoretical.
Terms defined, and further explanations:
A "standard pancake" is assumed to be 4" in diameter and however thick is normal for your batter. This allows for variations on batter consistency, a major concern when trying to determine the equation.
T= total cooking time
N = the number of pancakes you need to eat to make a decent meal.
C = the number of pancakes you can cook simultaneously in your pan
t = is the time it takes to cook a standard pancake.
d = average thickness of your standard pancake.
D = the thickness of the giant pancake
(N*4pi)/A = equation for the rate of increase in D by N. A being the area of the pan you plan on using for this. You can determine A from C by assuming the most efficient packing algorithm is used for the 4" pancakes, which will give you a range of sizes the pan could be. For C=1 the pan (P) has a diameter of 4" is less than P is less than 8". Thus for C=2 8" is less than P is less than 8.61", C=3 8.61" is less than P is less than 9.65", C=4 9.65" is less than P is less than 12" C=7 12" is less than P is less than 12"+.
If anyone manages to refine these numbers experimentally, do let me know.
**Edit: Changed the number of pancakes a 12" pan can use from 5 to 7, and uploaded a new spreadsheet that reflects that change.**