Shallot and mushroom white lasagna

Ingredients

• 6 round shallots, quartered
• 1 carrot, peeled and finely chopped
• 2 sticks of celery, finely chopped
• 2 tbsp butter
• 1 kg mixed mushrooms, sliced
• 4 garlic cloves, minced
• 2 tbsp oregano
• 4 sprigs fresh thyme
• 175g lasagne sheets
• 225g mozzarella, grated
• 50g Parmesan
• 50g butter
• 2 round shallots, finely chopped
• 2 cloves of garlic, finely chopped
• 50g plain flour
• 750ml whole milk
• 1 tsp Dijon mustard
• 200g Parmesan