Hello SmartBudgetCook_UK.
Making vareniki at home is a wonderful way to save money, but the dough sealing process requires precision. When vareniki open during boiling, it is usually caused by one of two factors: either the dough is too dry, preventing a secure bond when pinched, or flour and filling residue got onto the edges, acting as a barrier against adhesion.
To prevent this, ensure your dough has enough hydration—typically a ratio of about two parts flour to one part warm water with a pinch of salt. Knead it thoroughly for at least 8 to 10 minutes to develop the gluten network, which provides the necessary elasticity and strength. When shaping, make sure the edges are completely free of any potato, cottage cheese, or fruit filling before pressing them together firmly. You can also brush a tiny amount of water along the inner rim if the dough feels a bit dry. Finally, drop them into gently simmering water rather than a violent boil so they do not thrash against each other and break open.