What dishes are paired with agnolini in Mantuan cuisine?
The Google translation of this article was a bit rough, so I went through it for you and added some links to recipes and such. I hope this helps. I learned a bit myself. That Torta Sbrisolona shall be mine! 

The recipe for Agnolini doesn't call for stock, but I bet you could use it in that preparation as long as you reduce it enough. You don't want a runny filling.

Source. http://www.ristorantimantova.info/piatti-tipici-mantovani


  The Mantuan kitchen is closely linked with the history and traditions of its neighboring cities. The
  geographical location of Mantua, squeezed between Venice and Emilia
  Romagna, characterizes the kitchen. The ruling Gonzaga dynasty heavily
  influenced the culinary traditions of Mantua. The Mantuan kitchen is
  often referred to as "Of the Princes and the People" because it
  combines the refinement of Gonzaga kitchen with dishes typical of the
  peasant folk.
  
  Among the typical dishes of Mantua, the real backbones are the first
  courses.
  
  Among the dishes are the very Mantuan "Miller's
  Risotto",
  the
  Agnolini (picture)
  and Tortelli di
  Zucca,
  a true symbol of the delicious local cuisine.
  
  As for the main courses, the Mantuan cuisine offers both fish dishes,
  such as catfish, trout, pike and saltarei the famous Sauced
  Pike
  and meat dishes, such as roast beef, poultry and game, stews, pot
  roasts and boiled him.
  
  Another highlight of the delicious local cuisine are the cold cuts and
  sausages. In addition to the famous Mantuan salami, one must not skip
  a tasting of Ciccioli, the
  Gras
  Pistàs,
  the sausages used for Risotto alla
  Mantovana
  and, especially in winter,
  Cotechino.
  
  Equally famous are the DOP (“Denominazione di Origine Protetta” or
  "Protected Designation of Origin") Mantuan cheeses Grana Padano,
  Parmigiano Reggiano and Provolone and the condiment Mustard
  Mantovana.
  
  As for fruits and vegetables, country kitchens are famous for their
  cultivation of melons and pears.
  
  Desserts, along with the first course, are the real highlight of the
  Mantuan cuisine, such as La Torta
  Sbrisolona,
  La Torta delle
  Rose,
  and La Torta
  Elvezia
  
  We must also say a few words about Mantuan wines: Denominazione di
  Origine Controllata Lambrusco Mantovano red
  wine, Colli
  Morenici white wines, and Garda Colli Mantovani
  wines.