To make a 3D embroidery on mittens, you need... crocheted mittens and some bright yarn :)

Mine are below:

Draw the pattern you want, better use scale 1:1.

Or use mine :)
Start with strawberries. We need filler. Tear off 3 pieces. Roll balls, lay them on the mittens and carefully sew at the edges. Give the shape of the berries.

Take yarn.

And embroider this way:

Refresh with stems and leaves:

You can also add some flowers :) And beads!

Whan all is done, wash them in cool water delicately, dry.

After drying, you get this result: