1. Place the spinach in a large pan with the lemon juice and cook for 2 minutes until wilted. Drain off any juice and keep warm.
2. For the sauce. Season the fromage frais with the tarragon and a little salt and black pepper. Heat gently for 1-2 minutes until warm. Don’t boil or the fromage frais will separate.
3. To assemble. Place a slice of toast on each plate and cover with a slice of ham. Pile on the spinach and top with a poached egg. Spoon over the sauce and serve immediately.