Preheat the oven to 350/177C convection (or 325F/162C conventional) and line a cookie sheet.
Combine all the ingredients for the birthday cake crumbles in a medium bowl and mix them with a hand mixer until they form small clusters.
Spread the crumbs on the baking sheet and bake for about 10 minutes. Remove them from the oven, use a fork to break up the larger chunks and return them to the oven for about 3-5 minutes until they're a golden brown color.
Remove them from the oven and allow them to cool completely-they will crisp up as they cool- then break them into crumbs.
Once crumbs have cooled, in a large bowl, begin whipping 2 cups of heavy whipping cream until the cream forms stiff peaks.
Fold in the sweetened condensed milk, salt and vanilla extract into the heavy whipping cream mixture.
Spread half of the ice cream on the bottom of a pan. Top it with half of the birthday cake crumbles. Repeat with the second half but omit the brown butter on the top layer.
Add extra sprinkles and freeze for at least 4-5 hours (best overnight).
