Oatmeal Base:

1/2 cup (113 grams) unsalted butter, room temperature

1 cup (205 grams) light brown sugar

1 large egg

1 teaspoon pure vanilla extract

1 1/4 cups (165 grams) all purpose flour

1/2 teaspoon baking soda

1/4 teaspoon salt

2 cups (180 grams) old fashioned rolled oats, divided

Filling:

1 cup (240 ml) reaspberry jam or preserves (homemade or store bought)