It is the freezing that turns asparagus to mush, not the blanching. Well, obviously if you blanch asparagus to death, that will also turn it to mush. But the freezing process causes ice crystals to puncture the cell walls of the asparagus and that accounts for the mush.
Commercial freezers are able to flash freeze vegetables and other foods at extremely low temperatures. Because the foods are frozen so quickly, only small ice crystals form, and the cell walls are not damaged. So commercially frozen food, when thawed, should retain its flavor, texture, and color.
Face it, some foods freeze better than others. One book we have on freezing foods suggests using frozen asparagus only in casseroles and dishes where you expect a certain degree of mush.
Does that mean you should give up on asparagus? Not necessarily.
Is there anything you can do to freeze them more quickly? The first step would be to have the asparagus as cool as possible when you place them in the freezer. So after blanching, do plunge them in ice water, then keep them there until they are cold. Dry them completely, but don't dawdle. If you can get them colder in the refrigerator, put them there for a while. We would freeze them in a single layer on baking sheets (as we do with berries), in the coldest part of the freezer, then transfer them to heavy-duty freezer bags once frozen. We have identified where the cold air blows in our freezers and we would put the asparagus as close to that – or in the air flow – as possible. We would also only freeze a small amount at a time. The more non-frozen food you put in the freezer, the longer it takes to cool down again.
While it is not the main culprit, one source we found suggests that you blanch asparagus for only 1 to 2 minutes. Another option is not to blanch the asparagus at all. (GASP! Did you read that right?!?) You blanch vegetables to disable enzymes that cause them to degrade in the freezer. This essentially increases their freezer shelf life (their freezer life?). If you're going to consume the asparagus fairly soon – within about a month – you can skip the blanching step entirely.
Finally, cook the asparagus from the frozen state.
If you try all these methods and your asparagus is still to mushy for your taste, your only choices are to give up or save up for a blast freezer, which can freeze foods 12 times faster than a conventional freezer. We suppose you could also take a page from today's innovative chefs and get a tank of liquid nitrogen (at –321°F (–196°C) – and instantly freeze your asparagus, but that seems like a lot of trouble….