It isn't 'bad grammar' at all! In fact, it's a perfectly correct construction in which the adjective stands for 'the state of being + adjective'.
In the phrase 'Cook from frozen, the adjective 'frozen' refers to the state that the steak needs to be in when you start cooking it.
In the phrase 'Cook the steak until brown and crisp', the two adjectives refer to the state that the steak should be in when it's ready to eat. It is a neater version of 'Cook the steak until [it is] brown and crisp'.
This is a very common type of construction, especially when we're talking about food.