In a large bowl, beat the butter, brown sugar and maple syrup until well combined.
Add the egg and vanilla and beat until smooth.
Add the flour, baking soda and salt (stir them together first only if you want to) to the butter-sugar mixture and stir by hand until almost combined; add white chocolate and walnuts and stir just until blended.
Drop spoonfuls of dough (or roll rough walnut-sized balls) about 2” apart on a cookie sheet that has been sprayed with nonstick spray. Flatten each a little with your hand, just to give them a head start. Bake for 10-12 minutes, or until pale golden and set around the edges but still soft in the middle. Transfer to a wire rack to cool.