We present a multiparty session type (MST) framework with \emph{asynchronous
mixed choice} (MC).
We propose a core construct for MC that allows transient inconsistencies in
protocol state between distributed participants, but ensures all participants
can always eventually reach a mutually consistent state.
We prove the correctness of our system by establishing a progress property and
an operational correspondence between global types and distributed local type
projections.
Based on our theory, we implement a practical toolchain for specifying and
validating asynchronous MST protocols featuring MC, and programming compliant
gen_statem processes in Erlang/OTP.
We test our framework by using our toolchain to specify and reimplement part of
the amqp_client of the RabbitMQ broker for Erlang.