Place a large, heat-proof bowl over top of a small saucepan filled with about an inch of water. Bring the saucepan up to a boil, then reduce the heat to a simmer.
Place the chocolate chips in the bowl and allow them to melt slowly, stirring occasionally.
Once melted, turn off the heat and add the vegan milk. Mix well to combine, making sure the chocolate mixture is smooth.
Spread in an even layer over the filling layer. Garnish with a little fleur de sel if desired. Return to the fridge to set for an hour, or overnight.
To serve: using the parchment paper, remove the bars from the pan, and cut into 12 or 16 squares.
Store for up to a week in an airtight container in the refrigerator, or in the freezer for up to two months.