Preheat oven to 375 degrees Steam or boil cauliflower until crisp-tender, drain Remove excess water by squeezing cauliflower in towel or patting out moisture, set aside In sauce pan over medium heat add olive oil and saute onions until softened Add heavy cream to pan, lower heat and bring to simmer Break cream cheese into small pieces and add to pan stirring quickly Add fresh spinach, sausage, mustard and fresh garlic, pepper and salt to sauce pan Once all cream cheese is smooth, remove pan from heat Combine cream mixture with muenster cheese and 1 cup cheddar Stir quickly with spatula until smooth and add cauliflower Place into 8×8 baking dish and top with remaining 1/2 cup cheddar Bake at 375 for 15-20 minutes until boiling and cheese is brown