Commentaire sur Shabbat 1:10

כדי שיצולו – like the food of Ben Drosai (who, according to Rashi, was a pirate; see Talmud Shabbat 20a, s.v. קן דרוסאי) and would cook his food one-third through, and as such, it would be eatable but further, there was no decree made lest he stir the coals.

Meat, onion[s], and egg[s] may not be roasted unless they can be [fully] roasted while it is still day.
Bread may not be put into an oven just before nightfall, nor a cake upon coals, unless its surface can form a crust while it is still day. Rabbi Elazar says: there must be time for the bottom to form a crust.
In today’s mishnah we learn that Bet Hillel agrees with Bet Shammai that food may not be put into an oven on Friday in order for it to cook on Shabbat, unless it has already been fully cooked before Shabbat begins.
Note that in yesterday’s mishnah we learned of a case where Bet Shammai agrees with Bet Hillel and in today’s mishnah we learn of a case where Bet Hillel agrees with Bet Shammai.
We can explain both of these sections together, since they are both in essence the same halakhah. Bet Hillel does not allow food to be left in the oven if the food is uncooked lest someone rakes the coals in the oven in order to increase the heat and cook the food faster. Since unlike the items in the previous mishnayot, the person will want her food on the Shabbat itself there is a fear that she will do something to hurry the food’s cooking. Raking the coals is forbidden on Shabbat under the category of lighting a fire. Hence, to “keep one away from sin” it is prohibited to even have uncooked food in the fire.
Cooking cakes or bread involved placing them on the sides of ovens. The bottom would crust before the top. Rabbi Elazar is therefore more lenient. He allows leaving the bread in the oven as long as the bottom has already crusted over, which will be before the top.

חררה – a thick cake baked on coals

שיקרמו – at the beginning of its baking it forms a crust.

פניה – which was towards the atmosphere of the oven.

כדי שיקרום התחתון – which cleaves to the earthenware of the oven, which is baked first prior to the crust forming on its face towards the atmosphere of the oven, and with this it is sufficient. But the Halakha is not according to Rabbi Eliezer.