In a microwave-safe bowl or small saucepan, gently warm the milk and butter together until just lukewarm (about 60–90 seconds).

Stir until the butter is melted and the mixture is warm to the touch but not hot.

In the bowl of a stand mixer fitted with a dough hook (or paddle to start), combine the flour, instant yeast, salt, and granulated sugar.

Pour in the warm milk–butter mixture and add the egg and cake batter extract. Mix on low to medium speed for 2–3 minutes until a soft dough begins to form.

Add the sprinkles and mix briefly until evenly incorporated.

Transfer the dough to a lightly floured surface and knead for 10–15 minutes until smooth, elastic, and no longer sticky.

Lightly oil a medium-sized bowl and place the dough inside, turning once to coat. Cover with a kitchen towel or plastic wrap and let rise in a warm place for about 1 hour, or until doubled in size.

While the dough rises, prepare the filling. In a bowl, mix together the softened butter, granulated sugar, lemon juice, heavy cream, and vanilla extract until smooth and spreadable. Set aside.

Once the dough has risen, turn it out onto a lightly floured surface. Roll the dough into a large rectangle, keeping the thickness even.

Spread the filling evenly across the dough, reaching close to the edges.

Starting from the long side, roll the dough up tightly into a log.

Using dental floss or a sharp knife, cut the log into evenly sized rolls. Place them into a buttered baking dish, leaving a little space between each roll.

Cover and let rise again for about 1 hour, or until puffy and nearly doubled in size.

Preheat the oven to 350°F.

Bake the rolls for about 25–28 minutes, or until lightly golden and baked through. Remove from the oven and allow them to cool slightly.

In a bowl, whisk together the powdered sugar, heavy cream, and cake batter extract until smooth. Adjust the consistency with a splash more cream if needed.

Drizzle the glaze over the warm rolls.

Top with extra sprinkles for a fun birthday cake finish.

Serve warm for the softest texture.