Frozen kale just isn't the same.
The process of freezing and thawing ruptures vegetables' cell walls and makes them softer; while this is often a bad thing, could it eliminate the need to blanch kale before sautéing it?
To find out, we stemmed, washed, and dried raw curly kale and froze it for a few days. Thn we pulled it from the freezer and tried it in our recipe for Simple Sautéed Kale (which calls for the kale to be blanched before sautéing). We made a batch of the regular recipe for comparison.
The frozen-and-thawed raw kale was very wet out of the freezer, and it turned stringy and mushy (even after we squeeze it dry) when sautéed. The kale that we'd blanched, drained, and pressed dry according to the recipe was pleasantly tender and flavorful, not washed-out.
But the frozen-and-thawed kale was perfectly fine when added directly to our Quick Hearty Tuscan Bean Stew and blended into our Kale-Pineapple Smoothies—tasters barely detected a difference between raw and frozen samples.
The bottom line: Freezing and then thawing raw kale does indeed soften it, but it compromises the kale's texture. We don't recommend this technique if you are going to sauté the kale.