The reason for not mixing too thoroughly is to avoid gluten formation. Another reason for letting it sit (besides allowing the dry acid to dissolve and create more gas) is to allow the glutens to relax. Fewer and more relaxed gluten strands makes for a more tender pancake. Yet another way to get tenderness is to use softer flour. Softer flour is something you often see in Southern baked goods; and a big reason to like them.
Softer flour (softer than most of the AP you find in the US, anyway) is something you see in a lot of boxed mixes, and self rising flours. Again, one of the reasons to like them for certain purposes..
If you make your own mix -- and you should at least try it -- it's a good idea to mix some of your AP with some cake flour to have a softened AP for biscuits, pancakes, waffles and turnovers (like Yorkshire pudding) -- just about anything which doesn't need a lot of structure, including a lot of quick breads like pancakes.
If you start with a hard AP like King Arthur, you may even want to go 50/50. My usual ratio is about 2 parts AP to 1 part cake flour.
You want to avoid "Bread Flour" for making pancakes if at all possible.
Here's an excellent recipe for the dry side:
Ingredients:
4 cups AP flour (not KA)
2 cups cake flour such as Swan's Down
2 tbs + 1 tsp double acting baking soda (for fluffy, omit the extra tsp for regular)
1 tsp baking soda
3 tbs granulated, turbinado or light brown sugar
2 tbs malt powder (the type you use for malted milk)
1 tbs table salt
For the wet side, you want to keep your ratios very simple because (a) they're simple; and (b) they work.
For each cup of dry mix, add 1 egg, 1 cup of milk, buttermilk, yogurt, sour cream, etc., 1 tbs of melted butter. Nonfat milk products won't work as well as low-fat or whole milk products. If you use buttermilk or any of the cultured milks, it's likely you'll have to increase the amount by roughly a quarter. You may mix any of the dairy products with any other. For instance, when I use sour cream I thin it with some milk -- about 50/50 -- before adding in.
When you mix, if you mix in a bowl, always wets into dries -- never the other way around. In a shaker it doesn't matter.
Several people have made the point of not over mixing. No matter how you mix -- whisk, spoon, or shaker -- your final batter should be lumpy, but there should be no visible, dry flour. If you lift the batter with a spoon and pour a ribbon back onto the surface, it should leave a distinct and lingering trail. A good trick for teaching kids to cook is to have them right their nick names on the surface of the batter with a batter ribbon. The first letter should be almost faded away as they finish the last.
The batter should pour slowly. As a rule of thumb, the slower the batter pours the thicker the pancake. If your pancakes are too thick and crepe like, thin the batter -- and vice versa. There is no set, "right" amount. Don't confuse dryer with not over mixing. A dryer mix will make a thicker cake, but not better in any other way. Dryer + not over mixed, will make a higher, fluffier pancake.
If you want super-fluffy pancakes, sift the dry ingredients after measuring.
You can rest the batter for five minutes or even longer -- a couple of hours, covered in the fridge, is fine. The trick for longer holds is to use "double acting baking soda." The "double" part means that one of the dry acids is heat activated, and will not use itself up after a few minutes in solution. If you use a single actor, you lose the luxury of a long hold.
Pancakes adore medium heat. Make sure your griddle is thoroughly and evenly preheated to a touch too hot. Reduce the heat, grease the griddle, and pour a "tester" right in the middle of your griddle. It will not bake evenly, but the griddle will equilibrate. Give the tester to the dog, and start cooking pancakes.
Small and medium pancakes bake evenly and quickly. Large pancakes are more problematic, the edges cook faster than the centers. If you want a creamy-in-the-middle cake go large. If not, keep them on the small side. Just so you know.
Hope this makes sense,
BDL