In large saucepan over low heat melt margarine. Blend in cocoa powder.
Stir in honey, then marshmallows. Cook over low heat, stirring constantly, until marshmallows melt and mixture is smoothly combined. Remove from heat.
Stir in vanilla. Add cereal and peanuts (if using). Stir until well combined.
Press lightly into greased 2 L (9") square pan. Cool. Cut into bars.
In keeping with good allergy practices, we remind you to be aware of allergens and to check labels on any packaged goods used. This recipe has been tested using Kellogg's* products. Results with other products may vary.