Preheat oven to 350°F. Line baking sheets with parchment paper.
In a large bowl, cream together the butter and white sugar until light and fluffy.
Add the egg, egg yolk, and lemon flavoring. Mix until combined.
In a separate bowl, whisk together the flour, lemon pudding mix, baking soda, and salt.
Slowly mix the dry ingredients into the wet ingredients until a soft dough forms.
Fold in the white chocolate chips.
Dollop small spoonfuls of strawberry jam over the top of the dough. Do not fully mix it in.
Use a 2-ounce cookie scoop to portion the dough onto the prepared baking sheets, making sure each scoop picks up a little jam.
Try to keep most of the jam toward the tops or centers of the dough balls instead of along the sides.
Chill the scooped cookie dough for 30 minutes.
Bake for 15 to 18 minutes, or until the edges are lightly golden brown and the centers still look slightly soft.
Let the cookies cool on the baking sheet for several minutes before transferring to a wire rack.