Unable to catch message header in Kafka batch listener

Question

When I am sending a message to my Kafka listener, I am sending custom headers along with the message. I was following this https://memorynotfound.com/spring-kafka-adding-custom-header-kafka-message-example/

But since I have a batch listener this doesn't work. I have heard of KafkaHeaderMapper but I don't know how to implement it.

Can someone please show me with code how can I produce with my custom header and capture it on the listener side?

I am using SpringBoot with SpringKafka

EDIT 1

In my List messages, this is the data, My header is being added to the message itself. Why is this happening?

{
   "payload":"\"test\"",
   "headers":{
      "X-Custom-Header":"Sending Custom Header with Spring Kafka",
      "id":"18280539-fcd2-e08a-6b01-e80df430858a",
      "timestamp":1619500941341
   }
}