Step 1
Dissolve chicken bouillon in 1 tablespoon water.
Step 2
Melt butter in a skillet over medium-high heat. Saute onions in hot butter until soft 7 to 10 minutes.
Step 3
Place potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender about 20 minutes; drain and return potatoes to pot.
Step 4
Mash potatoes onion mixture 1 egg garlic chicken bouillon 1/4 teaspoon salt and pepper together until potatoes are smooth.
Step 5
Sift flour sugar baking powder and 1/4 teaspoon salt together in a bowl; make a well in the center. Stir oil and 2 eggs into flour mixture. Add 3/4 cup water and beat until dough is smooth and elastic. Divide dough into 5 balls.
Step 6
Preheat oven to 350 degrees F (175 degrees C). Lightly oil a baking sheet.
Step 7
Roll 1 dough ball out on a lightly floured surface into a very thin rectangle. Brush surface of the dough with oil. Place about 5 spoonfuls of the potato mixture in a line on the dough about 2 inches from the long edge. Roll dough around filling. Pinch one end of the roll. Use the edge of your hand to cut dough roll into 5 knishes and pinch the edges of each. Repeat for remaining dough balls and potato filling. Place knishes on prepared baking sheet and brush each knish with oil.
Step 8
Bake in the preheated oven until golden brown and dough is cooked through about 20 minutes.