Preheat oven to 350°F (180°C). Line baking sheets with parchment or silicone mats.

In a large bowl or stand mixer, cream butter and granulated sugar for 2–3 minutes until light and fluffy.

Add eggs, vanilla, and canola oil. Mix until just combined.

In a separate bowl, whisk flour and baking powder together, then gradually add to wet mixture on low speed. Mix until no streaks of flour remain.

Scoop dough into 3-tablespoon portions, roll into balls, and flatten slightly. Roll the edges in colorful sprinkles.

Arrange on prepared sheets about 2 inches apart. Bake for 9–11 minutes, until edges are lightly golden and centers appear set but soft.

Cool completely on the pan before moving or frosting.

Melt white chocolate chips in the microwave in 15–30 second bursts, stirring until smooth. Set aside to cool slightly.

In a large bowl, beat butter until pale and fluffy. Gradually add powdered sugar, alternating with small splashes of heavy cream.

Add cake batter flavoring, then slowly mix in the melted white chocolate until smooth and creamy.

Adjust consistency with extra cream (to thin) or powdered sugar (to thicken).