Borrowed from French, the noun viennoiserie means, literally, Viennese-style thing. This noun is from French viennois, meaning Viennese, itself derived from Vienne, French form of the name of the capital of Austria.

The noun viennoiserie designates, in both French and English:
– (as a mass noun or in the plural): baked goods or pastries of a type made with puff pastry or a leavened dough enriched with ingredients such as butter, milk, eggs, etc.;
– a bakery that makes and sells this type of baked goods;
– custom, behaviour or practice characteristic of Vienna or Viennese people.

This type of baked goods originated in Viennese cuisine, but was later influenced by, and associated with, French baking.

Viennese-style baked goods were introduced into France by the Austrian entrepreneur August Zang (1807-1888), who, in 1839, opened the boulangerie-pâtisserie viennoise, 92, rue Richelieu, Paris.

The opening of the boulangerie-pâtisserie viennoise was announced in several Parisian newspapers on Wednesday 6^th November 1839—for example in Le Moniteur parisien [10^th Year, No. 310, page 4] and in Le Charivari [8^th Year, No. 310, page 4].

And, in an article published in La Presse (Paris, France) of Saturday 23^rd November 1839 [4^th Year, page 2, column 3], the French author Delphine de Girardin (1804-1855) wrote, under the pen name of Vicomte Charles de Launay, that the boulangerie-pâtisserie viennoise was attracting the crowds.

The earliest French uses of the noun viennoiserie that I have found are as follows, in chronological order:

1-: From Exposition Alimentaire. XVIII. Pain de gluten aux eaux minérales, by Delpont, published in Le Panthéon de l’Industrie. Revue Hebdomadaire Internationale Illustrée des Expositions et des Concours (Paris, France) of Sunday 10^th June 1883 [9^th Year, No. 426, page 174, column 1]—M. Dassis, director of the Boulangerie Française et Hongroise (165, faubourg Saint-Honoré, Paris), had obtained a patent for bread made from gluten flour and mineral waters:

M. Dassis est puissamment outillé et organisé pour cette fabrication spéciale à laquelle sont affectés, dans son établissement, quatre fours installés exclusivement pour cette production et celle du pain français et de la viennoiserie.
     translation:
Mr. Dassis is powerfully equipped and organised for this special manufacturing for which are allocated, in his establishment, four ovens installed exclusively for this production and that of French bread and of viennoiserie.

2-: From a correspondence from Vienna, by Walter Vogt, published in Le Figaro (Paris, Fance) of Wednesday 11^th February 1885 [31^st Year, 3^rd series, No. 42, page 5, column 1]—the rogues’ ball in Vienna was an annual fancy-dress ball in which men were disguised as pickpockets, murderers, etc., and women as pétroleuses, vitriolisers, etc.:

Ce bal des gueux est une viennoiserie des plus originales.
     translation:
This rogues’ ball is a most original viennoiserie.

3-: From Le Progrès (Lyon, France) of Thursday 12^th May 1887 [28^th Year, No. 10,526, page 4, column 6]:

A vendre […] BOULANGERIE pâtisserie viennoiserie située dans une rue passagère.
     translation:
For sale […] BOULANGERIE patisserie viennoiserie situated in a busy street.

The earliest English uses of the noun viennoiserie that I have found are as follows, in chronological order:

1-: From a review of Die Fledermaus, an operetta by the Austrian composer Johann Strauss (1825-1899), performed at Sadler’s Wells on Saturday 17^th November 1934—review by Richard Capell, published in The Daily Telegraph (London, England) of Monday 19^th November 1934 [No. 24,802, page 8, column 3]:

Warwick Braithwaite conducted with the utmost spirit. So far from a lack of Viennoiserie in his style, there was, if anything, a little exaggeration.

2-: From the caption to the following photograph, published in The Tatler and Bystander (London, England) of Wednesday 8^th March 1944 [Vol. 171, No. 2,228, page 305, column 2]:

“We will remember Vienna steaks,
One of Lord Woolton’s supreme mistakes”

“Vienna Lingers On” is an amusing burlesque of all the Viennoiserie of yester-year, from Strauss to Ivor Novello. Hermione Gingold as Fritzi, the toast of the town, with Bonar Colleano and Richard Curnock as her admirers and Olive Wright as the maid

3-: From a review of Tales from the Vienna Woods (Decca), conducted by Willi Boskovsky, and of Mahler’s First Symphony (CBS), conducted by Bruno Walter—review by Spike Hughes, published in The Tatler and Bystander (London, England) of Wednesday 5^th June 1963 [Vol. 248, No. 3,223, page 615, column 2]:

Musical Viennoiserie like this doesn’t always travel well. Bruno Walter was virtually alone in being able to take it with him, and his ability to recreate a peculiarly bitter-sweet Viennese sound wherever he went made him the unrivalled conductor of Mahler.

The earliest English use that I have found of viennoiserie in the sense of baked goods is from the glossary appended to The Breads of France and How to Bake Them in Your Own Kitchen (Indianapolis: The Bobbs-Merrill Company, Inc., 1978), by the U.S. journalist, author and baker Bernard Clayton, Jr. (1916-2011) [page 274, column 2]:

Viennoiserie: Breads and pastries brought to France generations ago by workers from Vienna.

The earliest English use that I have found of viennoiserie in the sense of a bakery is from the following advertisement, published in the Los Angeles Times (Los Angeles, California, USA) of Tuesday 28^th October 1980 [Sherman Oaks Galleria Supplement: page 25, column 3]:

CHEZ THURIÈS
French Bakery & Viennoiserie
Baguettes, croissants, stuffed rolls
light pastries (Pâtisserie Nouvelle).