According to the Shulchan Aruch/Beit Yossef, in order for the cooking to qualify as Bishul Yisrael, a Jew must actively participate in the cooking process. This participation must involve the Jew either:
- Place the food directly on the fire or heat source.
- Stir/flip the food while it is on the fire. This must be done before the food is one-third cooked.
- A Jew igniting the flame only after the pot has already been placed by a non-Jew on a cooking element that was off.
Since this is the opinion of the Shulchan Aruch, this was adopted as practice and a standard for Sephardic Jews.
Ashkenazim follow the opinion of the Rama, who holds that it is sufficient for a Jew to ignite the fire or heating source. This indirect participation is considered enough of an involvement to qualify as Bishul Yisrael. As long as the fire remains lit, any food cooked thereafter is deemed Bishul Yisrael according to the Ashkenazic tradition.
This level of involvement however, does not suffice for the Shulchan Aruch. As brought down in his halachic works (see Shulchan Aruch 113:7).
This question is complex. The simplest and most textually accurate answer is no.
There are however Poskim that formulated leniencies that are applicable in very specific and limited scenarios. Even these Poskim agree that ideally (lechatchilah), such leniencies should not be relied upon.
A Sephardic Jew should strive to fulfill Bishul Yisrael in accordance with the standards mentioned in the Shulchan Aruch. (See Answer 3.)
Absolutely. While Ashkenazim consider igniting the flame as a sufficient involvement in the cooking process, a dish that was directly placed on the fire and cooked by a Jew (such as done according to Sephardic standards) is all the more so Bishul Yisrael!
Absolutely. In truth, some Ashkenazi Poskim notably the Gaon of Vilna do not rely on the approach of only igniting the flame. Other prominent Psokim such as the Chochmat Adam are of the opinion that ideally even Ashkenazim should follow the opinion of Shulchan Aruch. See Chelkat Biyamin (קי”ג ס”ז ס”ק ע”ט וכן בביאורים סד”ה וכן נוהגין)