Pumpkin soup ! Argiro Barbarigou

This Pumpkin soup will warm up your cold days!!
Ingredients
1½ kg yellow pumpkin
2 tbsp olive oil
1 big chopped onion
800 ml water or broth from chicken or meat
500 ml fresh milk or light cream
1tbsp butter
1 pinch of nutmeg
salt
pepper
1 fresh thyme
200 gr graviera cheese (half chopped in cubes
and half grated)
300 gr strained yogurt