Preheat oven to 325°F (160°C). Line baking sheets with parchment paper.

In a stand mixer, beat softened butter until creamy. Add powdered sugar and beat until light and fluffy, 1-2 minutes. Beat in vanilla and almond extracts.

In a separate bowl, whisk together flour and salt. With mixer on low, gradually add flour mixture to butter mixture. Mix just until a soft dough forms.

Add rainbow jimmies and mix on low for 5-10 seconds, or fold in by hand, until evenly distributed.

Shape dough using preferred method: form into logs, wrap, and chill for 2+ hours before slicing 1/4" thick, OR use a cookie press to form shapes directly on baking sheets.

Bake for 12-15 minutes, rotating pans halfway, until set and bottoms are lightly golden. Tops should remain pale. Cool 5 mins on sheet, then transfer to wire rack to cool completely.

For frosting: Beat softened butter until creamy. Add sifted powdered sugar, vanilla, and salt. Beat on low, then medium for 2-3 mins until fluffy. Add cream 1 tbsp at a time until spreadable.

Once cookies are completely cool, match pairs. Spread or pipe frosting onto flat side of one cookie and gently press a second cookie on top to form a sandwich.