For custom HTTP methods you need to do it in raw TCP. First connect, then use the TCP Send Read Http block and send the raw request using \r\n for every linebreak, for example
PROPFIND / HTTP/1.1\r\nAccept: */*\r\nAccept-Encoding: identity\r\nAuthorization: Basic <base64>\r\nDepth: 1\r\n\r\n
You need to use interpolated mode, and build the basic auth header manually (base64 encode the string with user:pass separated by a colon like that). Also terminate with two \r\n\r\n as you can see in my example. You will be given the response as a single string with everything inside so prepare for some manual parsing ^^