Preparation:

While your ravioli (or other pasta types) are boiling briskly for a few minutes (for specific required cooking  time please see packaging and subtract one minute…), put the butter in a saucepan, and allow to melt (not fry!) with the sage leaves, so the two ingredients will give flavour to each other.
If you want a runnier sauces and prefer to use less butter/less fat, add some milk.
When ravioli/pasta are cooked, place them in the saucepan and start the fire low, while mixing gently. Turn flam off, serve, making sure there is a spoonful of sauce and at least one leaf in each plate, then add parmigiano (preferably freshly grated). Voilà. (upps, a french word….).