Vegetable flowers

Remove the flowers asap, because the plant is putting all it's energy into flowering, also once it has flowered the plant will die off. Just snap off the flowers and hopefully the kale will produce more leaves instead. It's good to pull off the leaves too, it encourages more growth, especially right now as they are starting to grow strongly in this mild weather.

Lettuce is different, once it starts to flower (bolt) there really is no way of stopping it and all you can do is pull it up for the compost heap. With lettuce you need to be planting a few at a time in succession.