Cook the lentils in boiling water for 35 minutes. Strain the lentils and crush with a fork.
Preheat the oven to 375 degrees F. Grease a cookie sheet or line a cookie sheet with parchment paper.
In a bowl, cream the crushed cooked lentils, butter, and brown sugar together and then add the egg and blend. Add the flour, baking soda, and vanilla. Stir in the oats, slivered almonds, pumpkin seeds, and chocolate chips and mix well.
Drop the cookies by the spoonful onto the prepared baking sheet and flatten. Bake the cookies for 13 to 18 minutes and allow to cool on a baking rack.