Combine butter and sugars in a large mixing bowl and use an electric mixer to beat until light, fluffy, and well-creamed (about 2 minutes on high-speed).

Add eggs and vanilla extract and stir well until combined.

In a separate large mixing bowl, whisk together cake flour, baking powder, baking soda, and salt.

With mixer on low-speed, gradually stir dry ingredients into wet until completely combined.

Add chocolate chips and sprinkles and stir until well incorporated into the batter.

Cover bowl with plastic wrap and chill in the refrigerator for at least 30 minutes before proceeding. Prepare the frosting filling.

Place the butter in a medium-sized mixing bowl and use an electric mixer to beat until smooth.

Gradually add powdered sugar until completely combined.

Add vanilla and lemon juice and stir well.

Gently stir in sprinkles until incorporated.

Scoop frosting onto 1 Tablespoon-sized scoops and place on a wax paper or parchment paper lined baking sheet or plate (you should get 15-16 scoops) and place in the freezer to firm up while the dough finishes chilling (if dough is already finished chilling, leave it in the fridge and let the frosting freeze for at least 15 minutes). Meanwhile, preheat oven to 375F (190C).

Remove dough from refrigerator and scoop into 1/4 cup portions (83g) (if it's still too sticky to manage, just refrigerate longer). Roll between your palms until smooth then use your thumbs to make an indent into the center of the dough ball. Remove a scoop of the frosting filling from the freezer and press it into the center of the dough, then form the dough back around the frosting and gently form into a smooth ball. Repeat with remaining dough and frosting (you may have a scoop or two of frosting left over, this is fine).

Place cookies at least 2” (5cm) apart on parchment paper-lined baking sheet and transfer to center rack of 375F (190C) oven. Bake for 12-13 minutes. When finished baking cookies will still be quite pale on top but the very bottoms will be beginning to turn a light golden brown. (note: for thicker, rounder cookies, chill the assembled cookie dough balls for 15 minutes or longer before baking).

Allow cookies to cool for at least 15 minutes on baking sheet before transferring to cooling rack to cool completely before enjoying. If cut into while still warm, cookies will appear under-done in the center but will not if allowed to cool completely.