This paper proposes an essence-based method chunk metamodel. Method chunk is one of the terms used for method part in Situational Method Engineering (SME). SME is an engineering process to construct a new situational software development method which is composed from method parts. The method part can be extracted from any existing software development method which is described in various terms and notations. Applying SME in a software project will improve the quality of the software product, since it uses a project specific (or situational) method. The proposed metamodel is described using Object Management Group (OMG)'s standard for method modeling, called Essence Framework, which defines Essence Kernel and Language. Later, the proposed metamodel can be used by various method chunk providers as a guidance in method chunk modeling. Using OMG's standard in the method chunk modeling will increase interoperability in applying SME since method chunks from various provider will use the same notations. The elements of the proposed metamodel are defined based on existing method part metamodels. This metamodel also includes the context model as additional attributes of a situational method chunk. Essence kernel elements such as alpha, activity space, and competency are used to describe elements in the proposed metamodel. Evaluation of the proposed metamodel is conducted by checking the completeness of method chunk elements, and by instantiate essence-based method chunks using the proposed metamodel.