These squares have a buttery shortbread crust topped with candied fruit, then covered with that magic ingredient, sweetened condensed milk. It's a gooey, decadent treat so cut the pieces small.
Line a 9 x 13-inch baking pan with parchment. Move oven rack to center position and preheat to 375°F.
In a stand mixer cream butter and sugar together on high speed, about 3 minutes.
Whisk flour blend and xanthan gum to combine.
With mixer on low speed, slowly add flour in large spoonfuls. Mix until uniformly combined. It will look dry and crumbly.
Press into prepared baking pan smoothing the top with the bottom of a measuring cup or a smaller baking pan. Bake 12 minutes.
Turn oven down to 325℉ while completing the next steps.
Toppings
Sprinkle candied peel evenly over the partially cooked crust. Repeat with candied mixed fruit.
Pour wide ribbons of sweetened condensed milk over the entire surface being sure to go right to the edges and corners.
Sprinkle with sliced almonds.
Bake for another 25-30 minutes until bubbly and lightly browned around the edges. Cool completely. before cutting. Bars are always easiest to cut when cold.
Use parchment paper to transfer squares onto a cutting board. Use a ruler to cut 1½-inch squares, six across then nine on the long side. See NOTES below for tips.
Notes
*EGFG flour blend: 300g sweet rice flour, 300g potato starch, 200g sorghum flour, 200g millet flour (makes ~8 cups)To cut into perfect squares lay a ruler on top and make cut marks at 1½ inches intervals in one direction. Repeat at the opposite end so your cut line will be straight. Using a hot knife, wiped off after each cut, make all the cuts in one direction. Repeat in the opposite direction. There is typically one edge with pieces that are a bit smaller. They're for tasting or giving as Factory Seconds.The almonds make if difficult to cut them smaller but you could further cut each piece on the diagonal to have over 100 tiny bites.