I picked collards after the plants were in full bloom & when the seed pods were full.Even after the seeds fell to the ground in June. I pick my collard leaves, do not cut the stalk. I have 20 or so plants that are in there 3rd Spring & 48 that are in their second Spring.
I love collards year around, but that may just be me.
Lettuce does go to seed tasting bitter.
My mustard & spinach go to seed, I just pull them up to compost, never tasted them at that point.
I have tried growing Kale once, I will have to try your recipe next year.

We like kale flowers, and broccoli flowers as well, just tossed in salads.

I just picked a second crop of kale buds and stems, two weeks after the first crop. I snapped the stems off by hand, rather than cutting them. That allowed me to feel for the point where the stem is crisp, and just take that part of the stem. I just cut them into 2 inch lengths, boil them for a couple of minutes until they are tender, drain and stuff them into ball mason jars, and freeze them. They are delicious. Milder than mustard, no strong taste like broccoli. And no pests at all at this time of year. I'm going to grow Kale just for the buds and stems; I think they are much better than the greens.

I put them into stir fries - they are very mild.

Yep --we eat kale flowers and arugula flowers, mustard too -- really any brassica flowers, stems, buds, seed pods are all very tasty raw in salad or cooked. Nice to know you haven't let the brassicas go to "waste" just because you couldn't get to them before they bolted.

Radishes are also a brassica -- and if you let them bolt (they can get huge) and develop seed pods, the seed pods are quite a delicacy in salads.

I have 2 question for chinese kale (gailan)specifically.
(1) it's november fall season I planted chinese kale, they are 4 inches tall and flowers are appearing. Did they BOLT(meaning the end of the growing season for the plant?) or are they part of it as they grow. Anybody please give me an advise.
(2) How do you harvest them properly in order to last until late spring.?