Preheat oven to 350F degrees. Line 2 baking sheets with parchment paper.
In a bowl, combine the butter, brown sugar, granulated sugar, and corn syrup and stir until blended. Stir in the oats and nuts, mixing well.
To form the crisps, drop the oats mixture, about one tablespoon per cooking, rounded, onto the prepared baking sheets, spacing them about 2 1/2 inches apart.
Bake, rotating the baking sheets 180 degrees at the midway point, until golden brown and bubbly, about 13-15 minutes. Let cool for 5 minutes on the baking sheets. Then, using a metal spatula, transfer the crisps to a large flat plate or sheet of parchment to cool completely.
If topping with nuts after baked, place the nut on the cookies immediately out of the oven, pressing into the cookie gently.
If molding the cookies into cookie "taco", after cookies have cooled about 3 or 4 minutes, start to test the cookie with a metal spatula to see if it holds together. Once it is malleable, fold in half and place a measuring spoon or wooden spoon under the top fold to keep its shape until hardened and cooled.
If serving with creme fraiche or yogurt and fruit, place one cookie on a plate, add fruit and creme fraiche or yogurt and then top with second cookie. Sprinkle with lemon zest, if desired.