Set up a [cross-account IAM role](https://docs.aws.amazon.com/IAM/latest/UserGuide/tutorial_cross-account-with-roles.html) in the destination account
- Add a new IAM role
- For _type of trusted entity_ select "another AWS account"
- Specify the accountId of the account that will be using the resource in the destination account. You can find your AWS Account ID, which is available on the [support homepage](https://console.aws.amazon.com/support/home?region=eu-west-1#) when you are logged in.
- Create a policy that allows lambda:InvokeFunction for your function and attach it to this new role. 

Create a lambda in the calling account. 
- Set up a role for your lambda that is allowed to assumeRole
- Use the AWS SDK to assume the new role in the destination account. 
- Pass the credentials to the lambda object when you create it
- Invoke the lambda