Line a 9-inch by 13-inch baking pan with parchment paper leaving several inches overhanging on two opposite sides of the pan. Using a sharp knife or kitchen shears, cut marshmallows in half. Set aside.
Pulse graham crackers into fine crumbs in a food processor. Add ground flaxseed, powdered sugar, and salt. Pulse to combine. Empty into a large bowl.
By hand, with an electric mixer, or with a food processor, mix together until completely smooth the non-dairy butter, peanut butter, and vanilla. Pour into the bowl with graham cracker mix. Stir to combine. Empty out into the parchment-lined pan and spread evenly. Press firmly with your hands or roll a straight-sided glass over mixture. Place pan in the freezer while you prepare the chocolate layer.
In a double-boiler or in a microwave, melt chocolate, peanut butter, and coconut oil until chocolate is almost entirely melted. Remove from heat and stir to combine. The heat from the melted ingredients will continue to melt the remaining chocolate. Let cool slightly.
Remove pan from freezer and pour chocolate over and spread with an offset spatula or knife to smooth. Cover chocolate layer with rows of marshmallows by placing them cut-side down in the melted chocolate. Place pan in refrigerator for several hours or until chocolate has set. Set oven to broil on “HI”. Move a rack to highest location. Remove pan from refrigerator and place in oven just about 1 minute to brown marshmallows. Watch carefully! Alternatively, use a culinary torch to brown the marshmallows. Remove from oven and let cool for a few minutes or return to the refrigerator for 15 minutes if the chocolate layer feels soft. Carefully lift out the contents of the pan using the ends of the parchment paper. Cut into 2-inch squares. Serve chilled.
Is there a substitution I can use for ground flaxseed? I can only find whole flaxseed in my area, don’t have a high-speed blender, & neither my food processor nor my mortar & pestle are doing the trick!