Halve the pumpkin and cut into 8 slices. Remove seeds. Put the pumpkin loaf on a greased baking tray and bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 25 minutes.
In the meantime, wash the herbs, dab dry, pluck the leaves from the stems and chop them coarsely, except for a little basil for garnishing. Peel and chop the onion. Puree herbs, onion, oil and nuts in a blender.
Stir in the cheese. Season with salt, pepper and vinegar. Spread pumpkin slices with the pesto during the last 15 minutes of baking time. Arrange pumpkin slices with 1 slice of ham and 1 olive each.
Serve garnished with remaining basil.