"This is so good you'll slap yourself! Garnish with sliced almonds, if desired. This is excellent for teatime or to serve at parties or anytime you need a satisfying pick-me-up. Keep in a sealed container in the refrigerator for 6 to 8 weeks."
Place almonds in a bowl and cover with water; soak for 30 minutes. Drain water and peel almonds.
Blend peeled almonds in a food processor or blender until a paste forms; gradually add milk while continuing to blend. Add sugar and blend until smooth.
Heat butter in a skillet over medium heat; add almond mixture. Cook, stirring constantly, until mixture thickens and starts to pull away from the sides of the skillet, 10 to 15 minutes. Remove skillet from heat and add cardamom; stir for 1 to 2 minutes.
Butter a baking dish. Pour almond mixture into dish and spread into a 1/4-inch-thick rectangle. Cool for 15 to 20 minutes. Cut into squares or diamond shapes.