Peeping Mushroom Pasta

Ingredients

• 2 tablespoons butter
• 1/4 cup all-purpose flour
• 2 cups lukewarm milk
• 1/4 onion
• 1 whole clove
• 1 bay leaf
• 9 ounces rigatoni pasta
• Pinch of freshly ground nutmeg
• Sea salt and white pepper
• 2 tablespoons whole-grain mustard
• 3 1/2 ounces Gruyère, parmesan or other hard cheese
• 6 ounces mixed enoki or shimeji mushrooms
• Finely chopped fresh parsley for serving