פירוש על ברכות 69:1

HOW DOES ONE RECITE A BLESSING? The word כיצד literally, how, is usually used when the Mishna previously spoke of a rule or a mitzvoh that one is obligated to perform. Then the Mishna leads with the question, כיצד how is that obligation to be performed? Tosfos will explain why that does not apply to the law requiring that one recite b’rochos. It is not possible to ask here; to what previously mentioned ruling is the Tano referring when asking: how, as the Gemara asks at the beginning of this Maseches (2a), because here it is logical that there is an obligation to recite a b’rochoh, as the Gemara concludes that it is forbidden to benefit from this world without reciting a b’rochoh. Since it is logical that there is an obligation, the question: how, refers to this logic. There need not be a specific ruling in the Mishna to which the question is referring.
Alternatively, we can answer, that the question, how, refers to the Mishna in Mee Shemaiso (20b) that teaches a baal keree recites a b’rochoh after a meal, and does not recite a b’rochoh before a meal. The Mishna is clearly referring to an obligation to recite a b’rochoh. It is only saying that one does not recite that b’rochoh when a baal keree. And so too, here it is feasible to recite a b’rochoh on each and every thing; therefore the Gemara asks here, how one recites a b’rochoh that he is required to recite as we have seen in Mee Shemaiso.