Begin by adding the butter to a large pot. Melt the butter at medium heat. Stir occasionally so the butter doesn't burn.
Once the butter is melted add the water, corn syrup, and white granulated sugar. Stir to mix those ingredients together. This is will be the toffee base.
Heat the ingredients to 290 F/143 C. This is just slightly below the hard crack point. The mixture will turn from a pale yellow color to a nice beige color. Stir gently but constantly after the 200 F mark, again we don't want the base to burn. Use a candy thermometer.
After reaching the temp, turn the burner off and add in the slivered almonds.
Pour the toffee onto a buttered sheet pan and allow it to spread out level. I generally use an 11x17 inch pan for this. Sprinkle the chocolate chips on top and let it sit for 5 minutes.
Spread out the chocolate with a spatula thinly so it covers the top of the Almond Roca/toffee. Then sprinkle on the chopped roasted almonds.
Let it cool at room temp for about 20 minutes before placing it in the fridge to set completely, usually another 45 to 90 minutes. After it has set you can use a butter knife to break it apart. Enjoy! :)