Combine farmer cheese, Muenster cheese, eggs, and parsley in a bowl. Add salt; mix well.
Arrange phyllo dough lengthwise on a flat work surface; cut into 3 strips. Brush some butter lightly over 1 strip of phyllo. Cover remaining strips to keep them from drying out.
Spoon 1 teaspoon of the farmer cheese mixture on the edge closest to you; fold over 2 sheets of phyllo to make a triangle. Fold again to form another triangle; continue folding to the end of the strip. Brush top with butter. Repeat with remaining phyllo strips, butter, and cheese mixture. Transfer triangles to baking sheets.
Bake in the preheated oven until golden brown, about 20 minutes.
Farmer cheese is readily available on the East Coast but may be hard to find in the Midwest. Whole-milk ricotta is a fine substitute, but if you want to be authentic, you can always make farmer cheese. It's incredibly easy to make.