OKAY! The book is “Cordials from your Kitchen” by Pattie Vargas and Rich Gulling. They recommend that you toast 1 cup shelled black walnuts, then infuse with 1 cup 100 proof vodka and 1/2 cup bourbon for one month, shaking occasionally. Then you strain out the nuts. If you want to make a drinkable sweet liqueur add an equal amount (or to taste) of simple syrup; if you plan on using the extract for baking, you can use it as-is! Oh man, i think I have to make this now. it sounds amazing!