The recipe is a number of steps, which are functions that accept some data and output new, transformed or enriched data. Writing a recipe is one way to instruct Graphext on how to build a project/visualization given some tabular data (others being the use of the Wizard, or the application of pre-defined recipes). A recipe can have an arbitrary number of such steps. When you open the Recipe Editor, you will have done so having selected first a dataset that serves as the main input for the recipe. This dataset is made available by default with the name ds, and so the simplest possible recipe looks like 
create_project(ds)
i.e. a recipe with a single step called create_project which accepts a dataset as input and has no output. This is a special case. Since the result of this step is the creation of a project, it doesn’t generate any output that can be further processed inside the recipe. However, in practice you’ll almost always want to somehow transform or enrich your dataset and so you’ll want to add one or more of the many steps available in Graphext before the final step of project creation. A complete reference for all the steps available and how to use them lives under the API Docs