Preheat oven to 350°F. In a large bowl beat butter with a mixer on medium 30 seconds. Add both sugars, baking soda, and salt. Beat on medium 2 minutes, scraping bowl as needed. (Should be light and fluffy.) Beat in egg, egg yolk, maple syrup, and vanilla. Beat in sourdough discard. Beat in flour and spices. Stir in oats and currants.
Drop dough by tablespoons or a 1½-tablespoon cookie scoop 3 inches apart onto ungreased cookie sheets. Bake about 12 minutes per batch or until edges are golden brown. Cool on cookie sheet 2 minutes. remove; cool on wire racks.