Question: The Hotel Sacher's specialty of the house is a dessert invented by who?

Context paragraphs:
Hotel Sacher Salzburg: The Hotel Sacher Salzburg, Austria, is Salzburg's only grand hotel, a 5 star deluxe hotel.  The house is built in the style of the turn of the century, located on the shore of the Salzach in the centre and offers a view of the old town.  The hotel is located a few minutes away from the theatres of the Salzburg Festival.

Peach Melba: The Peach Melba (French: "pêche Melba" , pronounced ] ) is a dessert of peaches and raspberry sauce with vanilla ice cream.  The dish was invented in 1892 or 1893 by the French chef Auguste Escoffier at the Savoy Hotel, London, to honor the Australian soprano Nellie Melba.

Arctic roll: An Arctic roll is a British dessert made of vanilla ice cream wrapped in a thin layer of sponge cake to form a roll, with a layer of raspberry flavoured sauce between the sponge and the ice cream.  The dessert was invented in the 1950s, by Elva Hutchinson She set up a factory in Eastbourne producing Arctic Roll in 1968, and the dessert quickly became very popular.  During the 1980s more than 25 mi of Birds Eye Arctic Roll were sold each month.  However, sales slumped during the 1990s and eventually the manufacturer of Arctic Roll, Birds Eye, stopped producing the dessert.  The 2008 economic downturn saw the reappearance of Arctic Roll as consumers increasingly looked for low-cost foods.

Das Sacher: Das Sacher: In Bester Gesellschaft ("The Hotel Sacher: In the Bess Society") is an Austrian historical drama television series in two parts, directed by Robert Dornhelm and written by Rodica Doehnert, and based on the book "Das Sacher.  Geschichte einer Verführung" The series was commissioned by the ORF (broadcaster) and ZDF.  The first part was aired on December 27, 2016 on ORF2.

Mango pomelo sago: Mango pomelo sago is a type of contemporary Hong Kong dessert.  Invented in 1984 by , it has sustained its popularity up till now.  This dessert can be found in the menu of many Chinese restaurants and dessert stores in Hong Kong as well as Singapore and Taiwan.  As time goes by, this dessert has evolved into many different forms for the purpose of coping with the keen competition brought by other newly invented desserts.  For example, it serves as a flavour for other desserts and drinks.

Sachertorte: Sachertorte (] ) is a specific type of chocolate cake, or torte, invented by Austrian Franz Sacher in 1832 for Prince Wenzel von Metternich in Vienna, Austria.  It is one of the most famous Viennese culinary specialties.  5 December is National Sachertorte Day.

Hallo – Hotel Sacher … Portier!: Hallo – Hotel Sacher … Portier!  is an Austrian television series.

Elisabeth Gürtler: Elisabeth Gürtler-Mauthner (born May 7, 1950) is an Austrian businesswoman.  She is managing director of the Hotel Sacher, Vienna's most famous hotel.

Double skin milk: Double skin milk (Cantonese: 雙皮奶, soeng1 pei4 naai5) is a Cantonese dessert made of milk, egg whites, and sugar.  It was first invented in Shunde, Guangdong.  It is a velvety smooth milk custard somewhat resembling panna cotta, with two skins.  The first skin is formed during cooling of the boiled milk and the second when cooling the cooked custard.  Traditionally buffalo milk is used; its higher fat content compared to cow's milk produces a smooth texture.  This dessert is particularly famous in Shunde, Guangzhou, Macau, and Hong Kong.

Hotel Sacher: The Hotel Sacher is a five-star hotel located in the Innere Stadt first district of Vienna, Austria, vis-à-vis to the Vienna State Opera.  It is famous for the specialty of the house, the Sachertorte, a chocolate cake with apricot filling.  There is also an art gallery in the hotel with works from the 19th century.  The hotel is built near the former residence of Antonio Vivaldi.

Supporting paragraphs: Hotel Sacher Sachertorte
Answer: Franz Sacher