1. In a bowl, toss processed Cheddar, aged Cheddar and flour.
2. In a large saucepan or flameproof fondue pot, bring beer to a simmer over medium heat.
3. Reduce heat to medium-low. Add cheese mixture, a handful at a time, stirring constantly in a figure-eight motion with a wooden spoon until cheese is melted.
4. Stir in mustard and mix well. Add nutmeg, pepper and spinach and stir well. Remove from heat and set up on a fondue stand with a burner if desired. Serve with bread or other dippers.
Go to full version of