Problem with Baguette

My guess: the loaf is underdone.  Check the interior temperature of the loaf.  It should be 195 to 205° F (91 to 96°C).

Ford

This is what I would do with your formula:

Abandon the sugar. It looks like more yeast than I'd use. I might drop it back to 8 grams. Try and keep everything at a consistent temperature - maybe around 75 F.

Mix 200 g of flour with 200 g of water and a pinch (1/2 g) of yeast. Let this rest about 12 hours (poolish).

Mix poolish with the rest of the water and flour and gently mix until just combined - maybe a minute. Let this rest covered for 20 minutes.

Add the rest of the yeast and salt and mix again for about two minutes. Cover and rest an hour.

Do a series of stretch and folds. Cover and rest for an hour.

Divide your dough into 3 equal portions (weigh), shape into small cylinders and let rest 20 minutes.

Shape each cylinder into baguettes and let proof for about an hour in a couche. Preheat oven and pan for steam to 500F.

Place baguettes on parchment, stone or sheet and score each baguette. Do this just before you place the baguettes in the oven.

Place baguettes into the oven and pour a cup of boiling water into the steam pan. Steam for 10 minutes and remove steam pan.

Continue to bake for another 10 - 15 minutes to desired color.

Report back and let us know how it works out!

Jim

As already suggested get rid of the sugar there's plenty of starch in the flour and yeast is quite content eating that up. Reduce to less than 1% of yeast - btw if using fresh yeast a good amount is 0.8% and dry even less so assuming you are using dry yeast this (2%) is overkill. It seems your procedure is pretty decent but we have no idea how long you are proofing at each stage. Also (in my opinion) a sponge is not really worth the hassle especially if you have the patience to cold ferment as you get much better flavor from 12-24 hours of cold bulk fermentation. All that hooplah about nutty overtones is kind of urban legend and really only applicable if you are well experienced. So for sake of practicality its probably better to mix a bulk dough that much gluntenized and let it rise in the fridge. First do a 1.5 hour bench rise then put it away overnight in the fridge. In the morning divide and preshape then rest for 20 minutes. Next shape and final proof for about 40 minutes. Slash and bake in a very hot oven (no less than 480f) then send pics so the forum can better analyze your results !

For 3 loaves here's some suggested measures

600g Flour (ap, t55, t65 or whatever equivalent in your location)
420g water (70%) separate into two portions of 378g and 42g and do initial dough with the 378g

Autolyse after 4 minute mix for 20-30 minutes.

12g salt
5g fresh yeast (or whatever dry equivalent is which is less than 5g use a converter online)

Mix on slow for 8-10 minutes.

Add remaining 42g water and mix on high for 2-3 minutes until soft and extensible. If after 3 minutes it is still not separating from mixer continue mixing because this all depends on your flour but quickest should take only 2-3 minutes.

Divide into 3 portions each should weigh 350g