Preheat oven to 350° F. Grease a 9-inch tart pan with a removable bottom. Set aside.

Melt butter in a large saucepan over medium-low heat. Add the brown sugar and salt, stirring to combine.

Remove the mixture from heat and stir in egg and vanilla extract, mixing well. Add baking powder and baking soda, stirring until combined. Add flour and stir until just combined.

Place prepared tart pan on a baking sheet. Scrape the thick batter into the pan, spreading it as evenly as you can. Scatter chocolate chips over the top.

Bake until the center is just set, about 25 minutes. Place pan on a rack to cool before unmolding.

For the sauce, stir coffee and corn syrup in a saucepan over low heat until it begins to steam. Add chocolate, whisking until the mixture is just melted and smooth. Remove from heat and whisk in butter. If making ahead, store the sauce in the refrigerator and re-warm it over low heat.

To toast the almonds, heat them a wide skillet over medium heat, stirring frequently until fragrant and pale golden. Immediately transfer them from the hot pan onto a plate to prevent burning.

Serve Blond Brownie Tart slices with generous scoops of vanilla ice cream, Mocha Sauce, and toasted sliced almonds.