Traditional Polish Porcini Mushroom Dumplings - Homemade Uszka - Quickie Treats

Ingredients

• 250 g all-purpose flour, plus extra for dusting
• 130 ml very warm water
• 1 tbsp butter or 1½ tbsp oil
• ¼ teaspoon fine sea salt
• 50 g dried porcini mushrooms
• ½ onion, finely chopped
• 1 tablespoon vegetable oil, plus more for drizzling
• 1 tablespoon soy sauce
• 1 tablespoon breadcrumbs
• Salt and pepper to taste