Put the raisins and water in a large skillet. Cook slowly over low heat until tender, about 15 minutes.
Remove the raisins from the heat. Add the butter and let it melt through. Add the sugar, cinnamon, and salt and mix thoroughly. It will be a thick-liquid. Cool to lukewarm.
While the raisin mixture is cooling, preheat the oven to to 350°F (177°C). Line a cookie sheet with parchment paper or a nonstick silicone liner. (If you make large cookies, you may need to do 2 batches.)
Add the eggs to the raisin mixture. Mix the oatmeal, flour, and baking soda in a large bowl until well blended. Add to the raisin mixture. Blend well. Stir in the walnuts if using.
Drop by teaspoonfuls for small cookies or use a tablespoon for larger cookies, leaving about 1/2 inch between spoonfuls as the cookies will spread during baking.uncooked cookies on baking tray
Bake according to cookie size, about 10 minutes for small ones and up to 18 minutes for larger ones. Let cool briefly before serving. Store in airtight container.