Instructions

Grease the bowl of your slow cooker with cooking spray. Using two 4" to 5" strips of parchment paper, line bowl in an "X" formation. Using a hand mixer, beat butter and sugar until light and fluffy, about 2 minutes. Beat in egg and vanilla.
Add flour, baking soda, and salt and stir until fully combined. Fold in Cadbury eggs and white chocolate chips. Add cookie dough into slow cooker and smooth top with a spatula.
Cover and cook on high for 2 to 2 1/2 hours (or on low for 5 to 6 hours), until the cookie is almost completely cooked through and only slightly soft in the center.
Use the parchment paper to remove the cookie from slow cooker. Let cool.
In a large bowl using a hand mixer (or in the bowl of a stand mixer using the paddle attachment), beat butter until fluffy. Add powdered sugar and beat until combined, then add vanilla and heavy cream and beat until combined. (If you desire a thinner consistency, add 1 more tablespoon cream.) Add food coloring and mix until desired color is reached.
Transfer frosting to a piping bag fitted with a large star tip and pipe frosting around edge of cookie. Top with sprinkles.