In the bowl of the stand mixer with the paddle attachment, mix the soft butter and sugar together until light and fluffy.
Add in the egg and egg yolk and combine.
Add in the vanilla pudding and mix well.
Sift flour with the remaining dry ingredients and add to the mix. Keep on mixing on low speed just until combined.
Add in the sprinkles and combine.
Scoop the cookie dough and shape into balls. Put the cookie balls separated from each other on a baking tray with parchment paper. Press slightly every cookie before baking to help them spread more easily.
Bake on preheated oven at 180°C (355°F) for 12-14 minutes, until de edges look slightly golden and firm.