Preheat oven to 350 degrees Fahrenheit.

In the bowl of an electric mixer, cream butter and sugar. Then add eggs and vanilla and mix. Add sour cream and mix.

In a separate bowl, combine salt, baking soda and flour. Add to butter mixture, creaming until combined. Stir in sprinkles by hand.

Press/spread batter into a half sheet pan (18"x13") that you've lightly greased or sprayed with nonstick baking spray. Batter will be sticky, so do your best to spread it out evenly. Try using a spatula to spread it, and, if that doesn't work, use your hands. You may need to lightly butter your hands to prevent the batter from sticking to them.

Bake for approximately 14-15 minutes, or just until done. You don't want to see much browning around the edges, if any.

After the bars are cooled, make the frosting by creaming together butter, powdered sugar and vanilla with food coloring. Add milk slowly, mixing in between, until desired creamy consistency is reached. I used the full 1/4 cup, but you may not need to. Once it's creamy enough, turn mixer to medium-high speed and allow it to mix for 4 minutes. Frosting will be very smooth, creamy and fluffy afterwards! Spread onto cooled bars, then top with additional sprinkles. Slice into squares and serve.