Melt half the butter in a medium saucepan over a moderate heat and add the chopped garlic. Fry for 2 minutes until the garlic is just beginning to turn golden brown.
Add the cream, beans and nutmeg stirring to combine. Season well with salt and plenty of black pepper. When the mixture begins to bubble up reduce the heat to moderate low and simmer, stirring occasionally, for at least 5 minutes until the cream has thickened a little.
Add the spinach and cook for 2-3 minutes until just wilted then add the tarragon and mix well.
Melt the remaining butter in a cast iron frying pan over a moderate heat. Add the bacon and fry for 3-5 minutes until crisp and golden.
To serve, put a slice of toast rubbed with garlic on each plate, add the beans and top with the bacon and its buttery juices from the pan. Sprinkle with lots of black pepper and add a little lemon juice to the beans if wished.