In a large mixing bowl, combine the cake mix, melted butter (cooled), egg, and lemon juice. Beat until well-combined. Warning- dough will be very thick and sticky. Add 1 cup white chocolate chips to dough. Drop cookies by rounded spoonful onto a baking sheet covered with parchment paper. Bake at 350 for 7-9 minutes. Do no over-bake or white chocolate will become brown. Remove from oven and allow to finish cooking on baking sheets for 5 minutes. Cool cookies completely on a wire rack. For the topping, melt 1/2 cup white chocolate chips in a small crockpot. Spoon melted chocolate into a small plastic baggie. Snip corner off of bag and drizzle melted chocolate over the cooled cookies.