Kielbasa with Sauerkraut - Serving Dumplings

Ingredients

• 9 ounces mushrooms (sliced)
• 2 tbsp olive oil (or vegetable oil, divided)
• 1 tbsp unsalted butter
• 14 ounces kielbasa (sliced)
• 1 brown onion (thinly sliced)
• 2 garlic cloves (minced)
• ½ tsp salt (more to taste)
• ½ tsp black pepper
• ½ tsp ground cumin
• 1 tsp sweet paprika
• 1 tsp dried marjoram (or oregano)
• 1 tbsp tomato paste
• 1.1 pounds sauerkraut (drained)
• 1 bay leaf
• 1 cup apple juice