In a saucepan, bring the cream to a boil. in a separate heavy-bottomed saucepan placed over medium heat, melt 50 g. of the sugar. add another 50 g. of the sugar then continue in the same way with the rest of the sugar. cook just until the caramel develops a deep amber color. off the heat, add the butter in small pieces and stir to combine using a silicone spatula. stir in the hot cream in two parts. place the saucepan back over the heat and cook the caramel to 108 c. blend the caramel with an immersion blender, then pour it into a heat-resistant dish. cover and refrigerate to cool.