In a bowl, mix bread flour and cake flour. Add beaten egg, a pinch of salt, water, and vegetable oil. Mix until no dry flour remains. Knead until smooth. Cover with plastic wrap and let rest at room temperature for 30 minutes.

Grate the onion and garlic. Chop the parsley roughly.

In a bowl, combine all filling ingredients and mix well.

Roll the dough into a 20cm log and cut into 1cm pieces. Dust a surface with flour, place dough pieces cut-side up, and roll into 6cm circles. Repeat to make 20 pieces.

Place 1/20th of the filling onto each dough circle. Fold in half and pinch the edges to seal. Bring the ends together and pinch to form pelmeni. Repeat for all pieces.

Boil a large pot of water. Add pelmeni and cook over medium heat. Once they float, cook for an additional 3 minutes. Drain well.

In a bowl, toss the cooked pelmeni with salted butter until evenly coated.