Butter the inside of a 9" X 13" pan.
Melt the butter in a large pot over medium high heat, watching carefully as the solids start to brown. Once they brown, add the package of marshmallows and reduce the heat to medium; stirring constantly until the marshmallows melt.
Add the Rice Krispies and stir well to incorporate.
Portion out 1/4 cup of the Heath bits for garnish and incorporate the rest into the cereal mixture.
Pour into the greased pan and use your fingers to gently push into the corners and press lightly to make a firm bar. Allow to cool completely.
Remove from pan and cut into pieces; put on a rack over waxed paper.
Put the chocolate chips and half and half in a glass container and microwave in 30 second increments on low power. Remove after every 30 seconds and stir, adding more time as needed. DO NOT COOK ON MEDIUM OR HIGH HEAT. If the heat is too high, the chocolate will seize and be ruined; so slow is best. Will probably take about 2 minutes total. (Or melt with double boiler)
Use a fork or a pastry bag to top the treats with a chocolate drizzle.
Garnish with reserved toffee bits.