Heat the oven to 350° F / 176° C. Spread the walnuts on a small baking sheet and bake for 5 to 7 minutes

Until they have turned a shade darker and are fragrant. Let them sit until cool enough to handle

Then rub off as much of the thin skins as possible.

Transfer the walnuts to a marble mortar and pound to a coarse paste with the garlic. Add the basil and marjoram leaves and drizzle in the oil. Pound and stir with the pestle until thoroughly combined. Sprinkle in the sea salt and a few grindings of white pepper and stir well. Add the ricotta to the mortar by the spoonful

Stirring to incorporate it with the other ingredients. Once you have added all the ricotta

Give the pesto a vigorous stir to make it light and fluffy. Taste and add more salt and pepper if necessary.

Blitz the nuts to grind them up. Add the garlic

Salt and pepper and process or blend again. Add the ricotta and process/blend briefly to incorporate the ingredients. Transfer to a bowl and stir vigorously to incorporate air and make the pesto fluffy.

If not using immediately

Spoon the pesto into a container with an air-tight lid and refrigerate. Otherwise

If you're going to use the pesto as a sauce for pasta

Transfer it to a bowl and stir in 3 or 4 tablespoons of whole milk to loosen it.