Unit testing method which is using a private field initialized with static method

In my class TwitchService I'm creating a private field twitchClient using TwitchClientBuilder. How can I approach testing method sendChatMessage() which is using twitchClient?

public class TwitchService {

    public TwitchService(){
        twitchClient = TwitchClientBuilder.builder().build();
    }

    public void sendChatMessage(String content) throws Exception {
        if(content.isEmpty()){
            throw new Exception("Cannot send empty message!");
        }

        twitchClient.getChat().sendMessage(content);
    }
}

So far, I have tried mocking TwitchClientBuilder.builder() and twitchCliendBuilder.build() like this:

@RunWith(MockitoJUnitRunner.class)
public class TwitchServiceTest {

    private TwitchService twitchService;

    @Mock
    private TwitchClientBuilder twitchClientBuilder;


    @Test
    public void sendChatMessage() throws Exception {

        try (MockedStatic<TwitchClientBuilder> twitchClientBuilderMockedStatic = Mockito.mockStatic(TwitchClientBuilder.class)){
            twitchClientBuilderMockedStatic.when(() -> TwitchClientBuilder.builder()).thenReturn(mock(TwitchClientBuilder.class));

            when(twitchClientBuilder.build()).thenReturn(mock(TwitchClient.class));
            twitchService = new TwitchService("x", "y");
            twitchService.sendChatMessage("test message");
        }

    }
}

But I get NullPointerException on twitchClient in sendChatMessage() Any ideas how to properly mock fields like this?