"These three flavors are fundamental to our society," said Rahung Nasution, a Batak chef and adventurer who led me through the region.
Whisk in the yeast and egg; let stand until foamy, 10 minutes..In the bowl of a stand mixer fitted with the paddle, beat the 4 1/4 cups of flour and the salt at low speed just to combine.
With the machine on, slowly add the warm milk mixture and beat until incorporated, about 1 minute.Beat in 1 tablespoon of the butter until completely incorporated; scrape down the side of the bowl.Add the remaining 7 tablespoons of butter, 1 tablespoon at a time.
Beat the dough until well combined, about 2 minutes..Fit the mixer with the dough hook.
Knead the dough at medium speed until smooth, occasionally scraping down the side of the bowl and dusting with 1 to 2 tablespoons of flour if the dough sticks, about 5 minutes.
Transfer the dough to a lightly oiled bowl, turn to coat with oil and cover with plastic wrap.chopped fresh tarragon.
Working with one cucumber half at a time, use the side of a large knife to lightly crush the cucumber.Repeat with remaining cucumber halves.
Tear crushed cucumbers into chunks.. Whisk together oil, vinegar, shallot, and mustard in a serving bowl.Fold in crushed cucumbers, butter beans, and tarragon.