01 -
Set the oven temperature to 190°C (375°F) to prepare for baking.
02 -
In a mixer, beat the unsalted butter together with both brown and granulated sugars until the mixture is light and fluffy.
03 -
Add the eggs and vanilla extract to the creamed mixture and mix until fully combined.
04 -
Sift the all-purpose flour into a bowl, then add the rolled oats, baking soda, cinnamon, and salt. Mix to evenly distribute.
05 -
Pour the wet ingredients into the dry ingredients and stir until well blended.
06 -
Gently fold the chopped rhubarb, walnuts, and raisins into the batter to incorporate without overmixing.
07 -
Spoon the cookie batter onto a lightly greased baking sheet. Using the back of a spoon, flatten each mound to encourage even baking and prevent excessive thickness.
08 -
Bake in the preheated oven for 9 to 12 minutes, or until the cookies have golden edges and are crisp.