In Ceremony ch. 32 Spenser and Susan serve these along with Country pate sandwiches, which April finds disgusting. In Walking Shadow ch. 16 Spenser and his friends are working on the house in Concord and in addition to the store-bought sandwiches they have these sweet pickles.

Bread and Butter Pickles

16 cups (4 L) thinly sliced cucumbers
8 medium onions, peeled and thinly sliced 
1/2 cup (125 ml) pickling salt 
5 cup (250 ml) sugar
2 TBSP (30 ml) mustard seed 
2 tsp (10 ml) turmeric 
1 tsp (5 ml) celery seed 
5 cups (1.25 L) cider vinegar 

Mix the cucumbers and onions with the salt and 2 quarts (2 L) of
cracked ice and let them stand, covered with a weighted lid, for 3
hours. Drain thoroughly and put the vegetables in a large kettle.
Add the sugar, spices and vinegar and bring almost to a boil, stirring
often with a wooden spoon, but do not boil. Pack the pickles into
sterilized jars and seal. Makes about 4 quarts (4 L.)