Butter an 8x8-inch baking pan, line the bottom with parchment, and butter the parchment well. Don’t worry if the parchment pops up a bit, the weight of the caramel will press it back down. Scatter the nuts evenly over the bottom of the pan.
In a small saucepan, heat the cream with the vanilla over medium heat until it comes to a simmer. Reduce the heat to very low and keep the cream hot.
Heat the sugar with the honey in a 4-quart or larger saucepan over medium-high heat, stirring occasionally with a long-handled wooden spoon, until the sugar is mostly dissolved and it starts to boil, 4 to 5 minutes.
Stop stirring and brush down the sides of the pot with a clean pastry brush dipped in water to dissolve any clinging sugar crystals.
Clip a candy thermometer to the pot and let the mixture boil, without disturbing the bubbling sugar, until it reaches 305°F, 2 to 5 minutes. Rinse any clinging sugar off your spoon and dry it with a towel.
Add the 3 Tbs. butter and the salt. Slowly stir in the warm cream. The mixture will boil furiously and bubble up considerably as soon as you begin adding things: Just keep slowly and steadily pouring in the cream and stirring.
By the time all the cream is added, the temperature of the mixture will have started to drop. Continue stirring, watching the thermometer closely, until the temperature is back up to 250°F. Take the pan off the heat. Immediately pour the hot caramel into the prepared pan. Be sure to keep the pot moving back and forth as you pour so that the nuts don’t float away and congregate around the edge of the pan. Do not scrape the pot. What sticks to the pot should stay in the pot.
Set the pan on a rack in a cool part of your kitchen. Don’t disturb the pan until the caramel is fully cool and set, at least 5 hours, but preferably overnight.
Run a table knife around the edges of the pan and turn the caramel out onto an oiled cutting board. Peel off the parchment. With a chef’s knife, cut the caramel into 100 squares (about 3/4 inch each) and wrap them snugly in cellophane or other candy wrappers. Once cut, the caramels will slowly lose their shape, so it’s important to wrap them right away.
The wrapped caramels will keep for about four weeks if stored in an airtight container at room temperature.