× I made some pasta meanwhile Dora did the ironing.
√ I made some pasta while Dora did the ironing.
× I made some pasta. While, Dora did the ironing.
√ I made some pasta. Meanwhile, Dora did the ironing.
Meanwhile is an adverb, a connector, which means that it connects two independent sentences. We could say, ‘I made some pasta. Meanwhile, Dora did the ironing.’ In this case, ‘I made some pasta’ and ‘Dora did the ironing’ are independent sentences, and meanwhile is the connector, which shows that both actions happened at the same time. Meanwhile is normally used after a full stop (.) or a semicolon (;) and followed by a comma.
While is a subordinate conjunction, which means that the clause (subject + verb) which follows is not an independent sentence, it is a part of the main sentence. In the sentence ‘I made some pasta while Dora did the ironing’, we have the following structure: subject (I) + verb (made), object (some pasta), adverbial of time (while Dora did the ironing). While is never followed by a comma.
To see the difference between while and during, → see WHILE