Preheat oven to 350 degrees. Toast nuts on a baking pan for 10 minutes; remove from oven. Generously butter 5 baking pans. Arrange 5 pecan halves in a snowflake-shaped cluster, overlapping nuts in center. Repeat with remaining nuts, spacing clusters 2 inches apart.
In a heavy saucepan, combine corn syrup, whole milk, and sugar. Place over medium-high heat; cook, stirring occasionally with a wooden spoon, until syrup mixture comes to a boil, about 6 minutes. Stir in baking soda. Clip a candy thermometer to pan; add butter, stirring constantly until melted, keeping mixture at full boil. Slowly pour in evaporated milk; cook at a boil, stirring constantly, until temperature reaches 240 degrees (soft-ball stage), about 45 minutes. If pan starts to overflow, turn down heat for a few minutes; return to a boil.
Remove caramel from heat; transfer to a medium metal bowl. Cool to 200 degrees. Caramel will have the consistency of thick honey.
Using a spoon, gently mound 1 tablespoon caramel on top of each cluster. Allow caramel to harden. If caramel becomes too stiff, place bowl over low heat; stir constantly for several minutes until returned to proper consistency.
Temper chocolate following steps 1 through 3 in Chocolate-Nut Patties.
Drizzle 1 tablespoon of tempered chocolate over each cluster; set aside in a cool place to harden.
Store in an airtight container at constant room temperature for up to 1 month.