In "Recipe Context Null Objects in English", Massam and Roberge propose a set of rules for leaving out objects in what they call a "recipe context". It seems that rather than a new grammar, the recipe context is simply an abbreviated form of the English imperative structure that has come into popular use.
They give examples that are meant to demonstrate special handling of different sorts of verbs, such as (1), to show that perception verbs do not allow the object to be omitted.
(1) Put pan over high heat and add water. *See/*Hear ___ boil before adding other ingredients.
However, even if you do not omit the object, the imperative does not make a great deal of sense, as in (2). Instead, the recipe writer would say something like (3).
(2) Put pan over high heat and add water. *See/*Hear it boil before adding other ingredients.
(3) Put pan over high heat and add water. Let ___ boil before adding other ingredients.
They also provide the example shown in (4) to indicate that the EO can also serve as the antecedent of a reflexive, which is true, but only because the empty object is missing due to abbreviation, not due to actual removal from the sentence.
(4) Set out ___ on tray PRO to be served later.
They provide a number of examples where they try to remove objects from more complex sentences and are unable to do so, as in (5) and (6). It seems that these would be grammatically acceptable (particularly (6)), however they violate the convention of simple imperatives for writing recipes - these would appear in a terse cookbook even if they included the missing objects.
(5) Put cake in oven. *Expect ___ to be done half an hour later.
(6) *You must beat ___ well and cook ___ for 5 minutes.
In conclusion, it makes sense that the grammar used when writing recipes is basically the same as conventional English, except that it can be abbreviated by removing objects in places where they are understood. Objects cannot be easily removed from more complex sentences, or sentences that do not easily fit within the context of a recipe. In these cases, the recipe returns to narrative and uses conventional English.
References
Massam, Diane, and Yves Roberge. "On Recipe Context Null Objects in English". 1989. Linguistic Inquiry 20.1 pp 135-139.