Heat the olive oil and 1 tablespoon butter in a pan. Chop the garlic and parsley and roughly chop the tuna. Heat in the pan, stirring constantly. Whisk the egg yolks with the cream, stir in the Parmesan and finally melt and stir in the remaining butter. Cook the spaghetti al dente, drain and mix with the tuna sauce in the pan. Then mix in the egg cream.