This is not a pear i grow but it is well known as a high quality pear. Any pear that starts with the word beurre in it means buttery. Many of these european pears i research here
https://pomologie.com/poire/poire1/datapoir/europe.html
Sometimes we document these rare pears here Question the History of a pear or know some history? Post it here! but with thousands of pears out there we can’t track them all. Check this link for the extended list LESCRETS FRUITS ET POMOLOGIE LISTE des variétés de poires existantes