Baking – Freeze dried blueberries vs frozen blueberries

Once you've got your wet ingredients in there the timer is running. The chemical rising action only lasts a little while, and you want as much of that as possible to happen while the muffins are in the oven. If you wait past that window your muffins aren't going to rise very well, if at all, and I think you'd definitely run into that with freezing the mixture.

Even if freezing the batter would stop the chemical reaction (which I seriously doubt), you wouldn't be able to make use of that fact. Using a conventional freezer, the cooling process is going to be fairly gradual. Your batter is going to be at an active temperature for quite a while before eventually reaching the mythical non-reactive temperature--far longer than the chemical rising action lasts. And then as you thaw the batter you have another lengthy period where your chemical clock is ticking, long before you can get it in the oven.

In both cases, you don't add the recipe's amount of water to the proofed yeast. If your recipe says e.g. 500 g flour, 300 g water and 10 g fresh yeast, you measure these 300 ml water, then pour some of the 300 ml over 10 g of pressed yeast to proof it, adding a teaspoon of sugar if you want it quicker. After that, you mix flour, proofed yeast and the remaining water together (for simplicity, I left out salt and possible other ingredients).

You do it exactly the same way with dry yeast, only you have to use the correct substitute ratio, which is 3:1. So you measure 300 ml of water and (1/3)*10 g = 3.3 g of dry yeast. Then you pour some of the 300 g of water over the dry yeast, and after it has bloomed, you mix flour, sponge and the remaining water. The bread hydration stays correct, and the fermentation time/amount is equivalent to the fresh yeast case.