Rosemary hash browns with creamy mushrooms

Ingredients

• 4 red skin potatoes
• 1 egg
• 1 teaspoon celery salt
• 1 tablespoon chopped rosemary
• 1 tablespoon fine polenta
• 2 tablespoon olive oil
• 16 mini breakfast sausages
• 4 small red onions, halved
• 1 tablespoon olive oil
• 1 clove garlic, crushed
• 200 gram mixed mushrooms, sliced
• 1 cup cream
• 1 tablespoon wholegrain mustard
• sea salt and cracked pepper
• spinach leaves, to serve