Take 2 anchovies out of the can and cut them fine. Cut the butter into cubes. Add both into a stand mixer with a flat beater and mix at least 5 minutes until the butter is nice and fluffy.
Meanwhile, drain the tuna well. Add the sesame oil and pepper to the whipped butter and mix thoroughly through the butter.
Finally add the tuna and mix until it has been broken into threads through the whipped butter. This takes approximately 1 minute.
Serve with hearty bread or toast and caperberries.