Köttbullar med Gräddsås (Swedish meatballs with cream sauce)

Ingredients

• 10 tbsp heavy cream
• 5 tbsp breadcrumbs
• 1 onion
• 4 1/2 tbsp butter
• 14 oz ground venison
• 3 1/2 oz ground pork
• 1 egg
• 2 tsp salt
• 1 tsp mustard
• 1/3 cup flour
• 1/2 cup white wine
• 1 2/3 cups vegetable broth
• 1 bay leaf
• 1/2 tsp lemon juice
• vegetable oil (for frying)
• mashed potato (for serving)
• lingonberry jam (for serving)
• pepper
• salt