Line a baking sheet with parchment or wax paper and lightly dust with confectioners’ sugar. Combine the sugar, agave, water, butter, peppermint extract and vanilla in the bowl of a standing mixer and using the paddle attachment, beat on low speed. Increase the speed to medium-high and beat until very creamy, about 2-3 minutes.

Roll the peppermint mixture into a flat disk and place on the prepared baking sheet. Freeze until the peppermint is firm. Remove from the freezer and roll out about 1/4 inch thick. Using a cookie cutter cut mints to 1 ½ inch diameter. Cover and place in the refrigerator until the patties are firm at least one hour and up to overnight.

In a heatproof bowl placed over a saucepan of simmering water, melt the chocolate and the butter. Once the chocolate has melted, remove the bowl from the pan and whisk the chocolate and the butter until smooth. Insert a thermometer into the chocolate and cool to 80 degrees F.

Return the bowl to the pan of simmering water and reheat the chocolate to 88 to 92 degrees F. Remove the bowl from the pan.

Remove the patties from the refrigerator and dip, one patty at a time, into the melted chocolate, making sure both sides of each patty are completely coated with chocolate. You can use 2 forks or a chocolate dipping fork. Let any excess chocolate drip back into the bowl and then place the patties back on the foil. Once all the patties have been dipped in the chocolate, return to the refrigerator to chill until firm, at least 60 minutes.

Store in the refrigerator in an airtight container separate the layers with parchment paper or wax paper for up to one month.