Preheat the oven to 350. Coat the inside of a 9" springform pan with butter.
Brushing each sheet of phyllo dough with butter first, arrange them in the springform pan, being sure to come up the edges.
Bake the shell in a 350 degree oven for 5 minutes. Remove and let cool.
Combine the Castello aged havarti, cream cheese and sour cream in the bowl of a food processor. Pulse 5-6 times until blended.
Add the chives, garlic, lemon juice, salt and crushed red pepper flakes. Pulse until eveything is well combined.
Add the spinach and pulse again until just blended.
Spoon the filling into the shell, being careful to push it to the edges without breaking the phyllo.
Bake the cheesecake in the center of the oven for 60 minutes or until the center is just barely done.
Remove the cheesecake to a rack and let cool to room temperature before serving.
The cheesecake can be served cold, but is best when allowed to come to room temperature if stored in the refrigerator before serving.