Preheat the oven to 350°F. Cut a piece of parchment paper to fit a 9-inch cake round pan (spring form works well). Place parchment paper in the bottom of a 9- inch cake pan and light grease the sides but cookie spray.
Cream the butter, peanut butter and sugars together until fluffy and light. Next, beat in the egg and vanilla extract.
In a separate bowl, combine the flour, baking soda, baking powder, salt, and oats.
Add the dry ingredients to the butter mixture and mix until well combined. The batter will be pretty thick.
Next, stir in the M&MS and sprinkles.
Spread dough into the cake pan and place chocolate eggs on cake.
Bake for 18 minutes when the top and edges begin to brown. Remove cake from the oven and let it cool on the counter.
For Frosting:
Whip the butter and slowly add the powdered sugar and half cup at a time.
Add milk and continue to mix. Add an additional tablespoon of milk if needed to get a smooth and fluffy consistency. Ad a few drops of coloring of desired color.
Place frosting in a pipping bag or in a sealable bag. If using a sealable you will snip about ¼ in the corner to pipe the frosting. Remove cake from cake pan, and pipe frosting along the outside edges of the cake and garnish with remaining sprinkles.