Such dashboard was available in appmon. In dynatrace there is no such option. You can check method hotspots and see how many samples was recorded on particular method in selected timeframe. But samples does not mean exact value of executions.
If your java method is already a specific key request already as you mentioned, you should be able to see the throughput of the method in the Throughput tab of the particular service page. When on the throughput tab, you should be able to scroll down to the list of requests and see your particular key request and the Total number of requests. (See screenshot below). If this particular method is not a key request already and is very critical to monitor, you can create a custom service with the fully qualified class name as explained here. Then the methods selected in the custom service configuration will be monitored and can be marked as key requests.