I'm not really sure if there is a fixed definition for a miche. From what I can determine, from reading baking books and information posted on the Internet, there are numerous miche formulas, ranging from exclusively whole wheat to mixed-flour. Based on my limited research, one thing that seems to make them stand out from the crowd is their size---they're big. The legendary French baker Lionel Poilâne, who reintroduced the miche in Paris in the 1970s created his loaves using stone-ground flour, natural fermentation and a wood-fired oven. Mr. Poilâne's loaves weighed 2 kilograms each (4.4 lbs). I made mine approximately the same size. His were round, mine are oval, because, as you can see from the oven photo, that's the only way I could get these two big guys into my oven.
"Poilâne is most famous for a round, two-kilogram sourdough country bread referred to as a miche or pain Poilâne. This bread is often referred to as wholewheat but in fact is not: the flour used is mostly so-called grey flour of 85% extraction (meaning that some but not all of the wheat bran is retained). According to Poilâne's own website, the dough also contains 30% spelt, an ancestor of wheat." [Wikipedia]
After a number of iterations I've come up with a mix of flours that I like and, for my taste, has good flavor. I also incorporated a soaker in this version. Anyway, here's the latest iteration.
This recipe uses a double levain build, a total 14-18 hrs. total build, depending on room temperature (I used a tablespoon of mature culture, equal amounts all-purpose flour and water for each build (8 oz. water, 7 oz. flour)).
All the levain - 29 oz.
White all-purpose flour - 34 oz.
White whole wheat flour - 16 oz.
light rye flour - 7 oz.
Water - 35 oz.
Salt - 1.5 oz (2 Tb.)
Soaker (optional) 2 cups cracked rye
Total water = 51 oz (including levain)
Total flour = 71 oz (including levain)
Hydration = 71%
Note: Give the dough three (3) stretch and folds at 20 minute intervals. Then retard it in fridge overnight or for up to 20 hours before removing and bringing to room temp. After the dough reaches room temp. (approx. 2 hrs.) divide, shape and place in bannetons seam side up. Allow to nearly double in volume (finger poke test) and turn out of bannetons onto parchment lined baking pans sprinkled heavily with semolina flour. Score the loaves and bake in preheated (475 deg. over) with steam. After 10 minutes reduce heat to 450 deg. Bake for 40-50 min. Check for an internal temp. of [EDIT] 205-210 deg.
Cool on wire racks.