Calling async functions inside of WebSocket handlers

[ctron]

When implementing a websocket method for handling messages (@OnMessage), it is not possible to call something that blocks:

2022-09-06 14:15:12,046 INFO  [io.dro.iot.hac.eve.WebSocketEndpoint] (vert.x-eventloop-thread-3) Failed to handle message: java.lang.IllegalStateException: The current thread cannot be blocked: vert.x-eventloop-thread-3
	at io.smallrye.mutiny.operators.uni.UniBlockingAwait.await(UniBlockingAwait.java:30)
	at io.smallrye.mutiny.groups.UniAwait.atMost(UniAwait.java:65)
	at io.smallrye.mutiny.groups.UniAwait.indefinitely(UniAwait.java:46)
	at io.quarkus.security.runtime.QuarkusIdentityProviderManagerImpl.authenticateBlocking(QuarkusIdentityProviderManagerImpl.java:132)
	at io.quarkus.security.identity.IdentityProviderManagerCreator_ProducerMethod_ipm_91f102be1b2a781216db8a81e6ab4b9b1a84f03c_ClientProxy.authenticateBlocking(Unknown Source)
	at io.drogue.iot.hackathon.events.EventSession.handleAccessToken(EventSession.java:83)

However I cannot find any explanation how to run anything async (using a Uni) inside a WebSocket method.

Assuming I have a Uni, how can I subscribe to the outcome of the operation, so that it works in context with WebSocket. An example would be helpful to other too I guess.