- Disgorge the sweetbreads. To do this, place them in a bowl, cover with cold water and refrigerate for about 4 hours, changing the water two to three times. Drain.
- In a saucepan, cover the sweetbreads with salted water. Bring to a boil. Reduce the heat and simmer for about 5 minutes. Remove from the heat, rinse under cold running water and drain well. With your fingers, strip away as much as possible of the white membrane covering the sweetbreads and cut into 2.5- cm (1-inch) bites.
- In a saucepan of salted boiling water, cook the onions for about 3 minutes. Drain and rinse under cold water. Peel and cut the bigger onions in two.
- In a non-stick skillet, brown the sweetbreads in the butter for 4 to 5 minutes. Season with salt and pepper. Deglaze with the vinegar and add the honey. Cook for 1 minute. Keep warm on a plate.
- In the same skillet, brown the onions and squash in the oil. Season with salt and pepper. Deglaze with the wine and reduce until almost dry. Add the veal stock.
- Bring to a boil and simmer for 8 to 10 minutes or until the squash is tender. Add veal stock, if needed. Add the sweetbreads back in the pan with the spinach. Stir to combine. Adjust the seasoning.
Cipollini are small Italian onions that are mild and sweet.