1. Preheat oven to 375ºF. Line a 12-cup muffin tin with paper liners or coat with cooking spray. Combine flour, poppy seeds, baking powder and salt in a medium bowl.
2. In a large bowl, whisk together butter, sugar, eggs, almond extract and milk. Stir in flour mixture until just combined (mixture will be lumpy).
3. Fill each muffin cup with about 1/3 cup batter. Spoon 1 tsp. jam on top of each. Cover with remaining batter so each cup is almost full. Sprinkle with sliced almonds, if desired.
4. Bake until muffins are golden, about 20 minutes. Let cool in pan for 5 to 10 minutes, then remove from pan and let cool completely on rack.