Place the top oven rack in the center position and preheat oven to 350°F.

Spread the whole almonds in a single layer on a baking sheet and toast for 5–6 minutes.

Remove from the oven and push the whole almonds to one side of the sheet. Spread the sliced almonds on the other half in an even layer. Return to the oven for 4–5 more minutes. Remove and set aside.

Add the toasted whole almonds to a food processor and pulse until only a few small pieces remain. Set aside.

Melt 2 tablespoons butter in the microwave and set aside.

Line an 8×8-inch baking pan with a parchment paper sling. Brush the melted butter over the bottom and sides of the parchment.

Sprinkle half of the ground almonds in an even layer over the prepared pan. Set aside.

Melt ½ cup chocolate chips in the microwave, stirring every 20–25 seconds until smooth. Pour the melted chocolate over the almonds and spread evenly. Refrigerate just until set.

Add the remaining chocolate chips to the food processor and pulse until finely ground. Set aside.

In a large heavy saucepan set over medium heat, combine the remaining butter, sugar, water, and corn syrup. Stir until the butter melts, about 5–6 minutes.

Once the mixture begins to bubble, stop stirring. Attach a candy thermometer (keeping it from touching the bottom) and reduce heat slightly. Cook until the temperature reaches 290–295°F.

Remove from heat and immediately stir in the vanilla and baking soda. Pour the mixture into the prepared pan and tap gently to level.

Immediately sprinkle the ground chocolate chips over the top and spread as they melt into a smooth layer.

Sprinkle the remaining ground almonds and the toasted sliced almonds over the chocolate. Gently press to help them adhere.

Refrigerate 10–15 minutes, or just until set.

Lift out using the parchment sling, transfer to a cutting board, and break into pieces with the tip of a sharp knife.

Serve right away, or store in an airtight container in the refrigerator for 2–3 weeks.